Power Platform Custom Connector Creation#

Build production-ready Power Platform custom connectors and submit them to the microsoft/PowerPlatformConnectors GitHub repo. This skill covers Independent Publisher and Verified Publisher connector paths.

References: OPENAPI_EXTENSIONS.md | AUTH_PATTERNS.md | POLICY_TEMPLATES.md | CUSTOM_CODE.md | WEBHOOK_TRIGGERS.md | CERTIFICATION.md | EXAMPLES.md | COMMON_MISTAKES.md

---

First Step: Identify Publisher Type#

IMPORTANT — Ask the user before proceeding:

Before generating any connector files or certification guidance, ask the user:

"Are you building an Independent Publisher connector or a Verified Publisher connector?"

• Independent Publisher — You are a community member (MVP, developer, enthusiast) wrapping a third-party API you do not own.
• Verified Publisher — You are the service/API owner and want to publish your own connector.

The answer determines: directory structure, brand color, icon requirements, OAuth support, certification workflow, submission target, and connector title format. Tailor all subsequent guidance to the selected publisher type.

---

Quick Reference: Independent Publisher vs Verified Publisher#

AspectIndependent PublisherVerified PublisherWhoCommunity member (MVP, developer) — does NOT own the APIService owner — owns the underlying APIBrand color****Must be #da3b01Custom brand color allowedPR targetindependent-publisher-connectors/ on dev branchcertified-connectors/ on dev branchCertificationFree, reviewed by MS Connector Certification TeamFree, via ISV Studio registrationConnector tierPremium (automatic for external APIs)Premium (automatic for external APIs)PR requirementsScreenshots of 3 unique operations working in a FlowThorough API testing documentationOAuth redirectPer-connector redirect URI (mandatory since Feb 2024)Per-connector redirect URI (mandatory since Feb 2024)OAuth support****Not currently supported for certificationFully supported (AAD, Generic OAuth)Connector titleService name only (≤30 chars)Service name only (≤30 chars)IconGeneric icon assigned automaticallyCustom icon required (100×100 to 230×230 px, PNG, non-white/non-default background)Submission targetGitHub PR to microsoft/PowerPlatformConnectorsMicrosoft Partner CenterIdentity verificationVerified credentials via OneVet + Microsoft AuthenticatorPartner Center accountDeployment timeline~15 business days after approval (Friday deployments)~15 business days after approval (Friday deployments)Intro artifactintro.md included in PRintro.md packaged in submission zip

Decision rule: If you own the API/service, go Verified Publisher. If you're wrapping a third-party API you don't own, go Independent Publisher.

---

Getting Started#

Required Files#

Every connector directory must contain:

FileRequiredPurposeapiDefinition.swagger.jsonYesOpenAPI 2.0 (Swagger) definition — operations, parameters, responses, schemasapiProperties.jsonYesConnection parameters, brand color, auth config, policy templatesreadme.mdYesDescription, prerequisites, supported operations, credentials guideicon.pngOptionalConnector icon displayed in the designerscript.csxOptionalC# custom code for request/response transformation

Directory Structure#

text

PowerPlatformConnectors/
├── independent-publisher-connectors/
│   └── YourConnector/
│       ├── apiDefinition.swagger.json
│       ├── apiProperties.json
│       ├── readme.md
│       ├── icon.png          (optional)
│       └── script.csx        (optional)
├── certified-connectors/       (verified publishers)
├── custom-connectors/          (samples only)
├── schemas/                    (JSON Schema for validation)
│   ├── apiDefinition.swagger.schema.json
│   └── paconn-apiProperties.schema.json
└── templates/                  (starter templates)

Scaffold a New Connector#

bash

# Fork and clone the repo
git clone https://github.com/<your-fork>/PowerPlatformConnectors.git
cd PowerPlatformConnectors
git checkout dev

# Create connector directory
mkdir independent-publisher-connectors/YourConnector
cd independent-publisher-connectors/YourConnector

# Create required files (see EXAMPLES.md for complete templates)

---

Swagger Definition Structure (apiDefinition.swagger.json)#

Critical: Must be OpenAPI 2.0 (Swagger). OpenAPI 3.0 is NOT supported.

If your source API provides an OpenAPI 3.0 definition, convert it before importing:

bash

# Option 1: api-spec-converter CLI (requires Node.js)
npm install -g api-spec-converter
api-spec-converter --from=openapi_3 --to=swagger_2 openapi3.yaml > apiDefinition.swagger.json

# Option 2: Apimatic Transform (https://www.apimatic.io/transformer)
# Upload your 3.0 file → select Swagger 2.0 → download

After conversion, manually verify the output — automated tools may not handle all Power Platform–specific extensions correctly.

json

{
  "swagger": "2.0",
  "info": {
    "version": "1.0.0",
    "title": "My Service",
    "description": "Short description (30-500 chars). No words 'API', 'Connector', or Power Platform product names.",
    "contact": {
      "name": "Your Name",
      "url": "https://github.com/yourusername",
      "email": "you@example.com"
    }
  },
  "host": "api.myservice.com",
  "basePath": "/v1",
  "schemes": ["https"],
  "consumes": ["application/json"],
  "produces": ["application/json"],
  "securityDefinitions": {},
  "security": [],
  "paths": {},
  "definitions": {},
  "x-ms-connector-metadata": [
    { "propertyName": "Website", "propertyValue": "https://myservice.com" },
    { "propertyName": "Privacy policy", "propertyValue": "https://myservice.com/privacy" },
    { "propertyName": "Categories", "propertyValue": "AI;Business Intelligence" }
  ]
}

Key rules:

• title — Maximum 30 characters. Cannot include the words "API", "Connector", "Copilot Studio", or any Power Platform product names. Must end with an alphanumeric character (no trailing punctuation, spaces, or special chars). Must be unique and distinguishable from existing connector titles. Note: the (Independent Publisher) suffix goes on the PR title, not the connector title in the OpenAPI definition
• description — Must be 30-500 characters for certification quality and must stay within the platform import hard limit of 1000 characters. Use plain text only (no HTML tags). Cannot contain "API", "Copilot Studio", or Power Platform product names. Must be free of grammatical and spelling errors. Should concisely describe the main purpose and value of the connector
• contact — Include name, url, and email with a valid email address
• x-ms-connector-metadata — Required array with Website, Privacy policy, and Categories. The Categories value must be a semicolon-delimited string from these allowed values: AI, Business Management, Business Intelligence, Collaboration, Commerce, Communication, Content and Files, Data, Finance, Human Resources, Internet of Things, IT Operations, Lifestyle and Entertainment, Marketing, Productivity, Sales and CRM, Security, Social Media, Website
• consumes / produces — Always explicitly set to ["application/json"] for JSON APIs. Do not omit these fields even if the API only handles JSON — being explicit prevents content-type mismatches
• schemes — Must include "https" (HTTP not allowed for production connectors)
• host — Production host URL only. Staging, dev, and test host URLs are not allowed. Base hostname only, no path segments

File formatting:

• Use soft tabs with 4 spaces for indentation — no hard tabs
• Remove trailing whitespace from all lines
• Structure the file in this order: swagger version → info → host/schemes → consumes/produces → paths → definitions → parameters

---

Operations (Paths)#

Define actions and triggers in the paths object:

json

"paths": {
  "/items": {
    "get": {
      "operationId": "ListItems",
      "summary": "List all items",
      "description": "Retrieves a list of all items from the service.",
      "x-ms-visibility": "important",
      "parameters": [
        {
          "name": "status",
          "in": "query",
          "type": "string",
          "x-ms-summary": "Status",
          "description": "Filter items by their current status.",
          "x-ms-visibility": "advanced"
        }
      ],
      "responses": {
        "200": {
          "description": "Success",
          "schema": { "$ref": "#/definitions/ItemList" }
        },
        "400": {
          "description": "The request was invalid or malformed."
        },
        "404": {
          "description": "The requested resource was not found."
        }
      }
    },
    "post": {
      "operationId": "CreateItem",
      "summary": "Create an item",
      "description": "Creates a new item in the service.",
      "parameters": [
        {
          "name": "body",
          "in": "body",
          "required": true,
          "schema": { "$ref": "#/definitions/CreateItemRequest" }
        }
      ],
      "responses": {
        "201": {
          "description": "Created",
          "schema": { "$ref": "#/definitions/Item" }
        }
      }
    }
  }
}

Key rules:

• operationId — Must be PascalCase (capitalize every word), unique across all operations. Remove all non-alpha characters — no hyphens, underscores, or spaces (e.g., get_user-info → GetUserInfo)
• summary — Required for every operation. Must be sentence case, 80 characters or fewer, and must end with an alphanumeric character (no trailing punctuation, spaces, or special characters). Must contain only alphanumeric characters or parentheses — no slashes ( /). As a naming convention: start with "List" when the operation returns multiple records, "Get" when it returns a single record. For triggers, use the format: "When a [event]" (e.g., "When a task is created")
• summary and description must not have the same text — the description should provide additional information beyond the summary
• description — Required for every operation and parameter. Must be a full, descriptive sentence ending in punctuation. Must not contain URLs or HTML markup. Must be in English and free of grammatical or spelling errors
• Input description UX style — Parameter descriptions are shown as helper text in Power Automate/Power Apps. Keep them concise and action-oriented: avoid repetitive prefixes like "Filter the response by"; prefer short forms like "Location code (ISO-3).", "Reference period start (inclusive).", or "Select from dropdown." for long enum lists

Description Style Examples (Parameters)#

Use this quick mapping when rewriting parameter helper text for designer UX.

PatternAvoidPreferGeneric filter prefixFilter the response by location code.``Location code (ISO-3).Date lower boundFilter entries to include rows where the reference period overlaps with or extends beyond this date...``Reference period start (inclusive).Date upper boundFilter entries to include rows where the reference period overlaps with or begins prior to this date...``Reference period end (inclusive).Boolean flagThe has_hrp flag. The has_hrp flag indicates whether...``Whether the location has a Humanitarian Response Plan (HRP).Enum (short list)... available values are described in documentation.``Allowed values: csv, json.Enum (long list/dropdown)Allowed values: value1, value2, value3, ...``Select from dropdown.Non-clickable referencesSee https://... for details.``See location metadata.

• x-ms-summary — Required on every parameter and schema property. Use Title Case, matching the parameter name but without hyphens or underscores (e.g., name: "form_name" → x-ms-summary: "Form Name")
• x-ms-visibility — Controls visibility: "important" (always shown), "advanced" (hidden under menu), "internal" (hidden from user)
• Response schemas — Each operation should have only one response with a schema, which should be the 2XX success response (200 or 201). The default response should NOT have a schema definition — schemas belong on expected success responses only. For error responses ( 4xx, 5xx), provide meaningful descriptions but remove the schema property. Empty response schemas are not allowed (except when dynamic). Empty operations are not allowed — every operation must have at least one response
• Boolean filters — Parameters that represent true/false flags (for example has_hrp, in_gho, is_hxl, and origin/asylum variants) should use "type": "boolean" instead of "string"
• Path parameters — All path parameters (e.g., /items/{itemId}) must include "x-ms-url-encoding": "single" and must be marked "required": true
• Reserved names — A parameter cannot be named connectionId (reserved by the platform)
• Swagger 2.0 parameter typing — Every non-body parameter ( in: query, header, path, formData) must include a type field. Missing type frequently causes APIM import failures such as JSON is valid against no schemas from 'oneOf'
• GET operations — Cannot have body or form data parameters
• collectionFormat: "multi" is NOT supported — The Custom Connector wizard rejects array parameters with "collectionFormat": "multi". Workaround: change the parameter type from array to string, accept comma-separated values, and use custom code ( script.csx) to split them into repeated query parameters. See CUSTOM_CODE.md Pattern 5 and COMMON_MISTAKES.md entry #33
• Remove empty properties from operations and parameters unless they are explicitly required

Recommended preflight lint before pac connector create / pac connector update:

• Confirm every non-body parameter has a type
• Confirm every action/operation has a non-empty description
• Confirm path parameters are required: true with x-ms-url-encoding: "single"
• Confirm each operation has exactly one success response schema
• Confirm every definitions.*.properties.* entry has an explicit schema discriminator ( type, $ref, enum, anyOf, oneOf, or allOf) so properties are never ambiguous during WADL conversion
• Confirm every array schema has explicit items typing/ref metadata (no "items": {} placeholders)
• Confirm no readOnly: true schema properties are listed in any definition required array
• Confirm there are no empty parameter/response/schema objects such as {} after automated transforms
• Confirm boolean-like flags ( has_*, in_*, is_*) are typed as boolean where semantically correct
• Confirm parameter descriptions are concise helper text (no repetitive "Filter the response by" boilerplate)
• Parse-check the file before deploy ( python -c "import json;json.load(open('apiDefinition.swagger.json',encoding='utf-8'))") to catch malformed JSON and trailing/extra data
• Check for missing operation descriptions ( python -c "import json; s=json.load(open('apiDefinition.swagger.json',encoding='utf-8')); missing=[(m.upper(),p,o.get('operationId')) for p,ms in s.get('paths',{}).items() for m,o in ms.items() if isinstance(o,dict) and not (isinstance(o.get('description'),str) and o.get('description').strip())]; print('missing_description_count',len(missing)); [print(x) for x in missing[:200]]")
• If converting from OpenAPI 3.x, run a second pass to ensure nullable fields were translated into valid Swagger 2.0 schemas (avoid leaving properties with only description/ title)
• Confirm nullable primitives use Swagger 2.0-compatible patterns ( type + x-nullable: true) and avoid OpenAPI 3 style unions like "type": ["integer", "null"]

---

Definitions (Schemas)#

Define reusable data models in the definitions object. These are referenced via $ref in operation parameters and responses.

Key rules:

• All objects under properties must include both a description and title property, even when nested — unless the object contains a $ref property
• Every property schema must include an explicit schema discriminator ( type, $ref, enum, anyOf, oneOf, or allOf); do not leave property definitions as metadata-only objects
• title — Must be in Title Case. Must not contain URLs
• description — Must be a full sentence with proper punctuation. Must not contain URLs
• Keep all other existing properties of the definition intact
• Remove default values from objects inside properties (defaults belong on operation parameters, not schema definitions)
• If a number or integer property's description mentions minimum or maximum values, add explicit minimum and/or maximum properties to the schema
• Nullable fields (Swagger 2.0) — Represent nullable scalar properties with x-nullable: true on the property schema. If upstream data can omit or null a field, remove that field from response required arrays. Do not use array type unions such as ["integer", "null"]

json

"definitions": {
  "Task": {
    "type": "object",
    "properties": {
      "id": {
        "type": "string",
        "title": "Task ID",
        "description": "The unique identifier for the task.",
        "x-ms-summary": "Task ID"
      },
      "name": {
        "type": "string",
        "title": "Task Name",
        "description": "The display name of the task.",
        "x-ms-summary": "Task Name"
      },
      "priority": {
        "type": "integer",
        "title": "Priority",
        "description": "The priority level of the task, from 1 (highest) to 5 (lowest).",
        "x-ms-summary": "Priority",
        "minimum": 1,
        "maximum": 5
      },
      "project": {
        "$ref": "#/definitions/Project"
      }
    }
  }
}

Note: The project property uses $ref, so it does not need its own title or description.

---

OpenAPI Extensions Quick Reference#

ExtensionPurposeApplies TosummaryAction title in designerOperationsx-ms-summaryDisplay name for entityParameters, schema propertiesdescriptionVerbose explanationOperations, parameters, schemasx-ms-visibility``important / advanced / internalOperations, parameters, schemasx-ms-trigger``"single" or "batch" — marks as triggerOperationsx-ms-trigger-hintHint text for triggersOperationsx-ms-notification-contentWebhook payload schemaResources (path level)x-ms-notification-urlMarks field as callback URLParametersx-ms-dynamic-valuesPopulate dropdown from API callParametersx-ms-dynamic-listEnhanced dynamic dropdown (unambiguous refs)Parametersx-ms-dynamic-schemaDynamic schema from API callParameters, responsesx-ms-dynamic-propertiesEnhanced dynamic schema (unambiguous refs)Parameters, responsesx-ms-capabilitiesTest connection, chunk transferConnectors, operationsx-ms-api-annotationVersioning: family, revision, replacementOperationsx-ms-url-encoding``"double" or "single" for path paramsPath parametersx-ms-connector-metadataWebsite, privacy policy, categoriesRoot levelx-ms-no-generic-testSkip generic testingOperationsx-ms-safe-operationMark POST as non-modifyingOperations

Copilot Studio / AI extensions:

ExtensionPurposex-ms-name-for-modelLLM-friendly operation name (snake_case)x-ms-description-for-modelLLM-friendly usage descriptionx-ms-media-kind``"image" or "audio" for media operations

Extended format types: date-no-tz, email, html, uri, uuid

See OPENAPI_EXTENSIONS.md for detailed examples of each extension.

Dynamic Dropdown Pattern (Metadata Endpoints)#

For connectors with metadata operations (for example, location/sector/org catalogs), use x-ms-dynamic-values so users can select valid values from dropdowns.

json

{
  "name": "location_code",
  "in": "query",
  "type": "string",
  "required": false,
  "x-ms-summary": "Location Code",
  "description": "Filter the response by location code.",
  "x-ms-dynamic-values": {
    "operationId": "GetLocationApiVMetadataLocationGet",
    "parameters": {
      "output_format": "json",
      "limit": 10000,
      "offset": 0
    },
    "value-collection": "data",
    "value-path": "code",
    "value-title": "name"
  }
}

Guidance:

• Map frequently reused filters (location/admin1/admin2/sector/org/org-type/commodity/market) to metadata operations
• Use value-collection to match the response payload root (commonly data)
• Avoid applying dynamic-values on the same metadata source action itself
• Provide stable defaults for source operation parameters ( output_format, limit, offset)

---

Authentication Quick Reference#

Configure auth in apiProperties.json under connectionParameters (or connectionParameterSets for multi-auth):

Auth Typetype valueIdentity ProviderExampleAPI KeysecurestringN/AMost Independent Publisher connectorsOAuth 2.0 (AAD)oauthSetting``aadAzure services (Key Vault, Graph)OAuth 2.0 (Generic)oauthSetting``oauth2 / oauth2genericGitHub, Slack, SpotifyBasic Authsecurestring (x2)N/AUsername + passwordMulti-AuthconnectionParameterSetsMixedMultiple auth options for one connector

Note: Multi-auth connectors use connectionParameterSets instead of connectionParameters and are not supported in the Custom Connector Wizard — use the pac connector or paconn CLI.

API Key example (apiProperties.json):

json

{
  "properties": {
    "connectionParameters": {
      "api_key": {
        "type": "securestring",
        "uiDefinition": {
          "constraints": { "clearText": false, "required": "true", "tabIndex": 2 },
          "description": "Your API key from the service dashboard",
          "displayName": "API Key",
          "tooltip": "Provide your API key"
        }
      }
    },
    "iconBrandColor": "#da3b01",
    "capabilities": [],
    "publisher": "Your Name",
    "stackOwner": "Service Company Name"
  }
}

Critical: Independent Publisher iconBrandColor must be "#da3b01".

See AUTH_PATTERNS.md for OAuth 2.0, AAD, and Basic Auth patterns.

---

Policy Templates#

Policy templates transform requests/responses without custom code. Defined in apiProperties.json:

Template IDPurposedynamichosturlRoute to dynamic host URL from connection paramssetheaderInject request/response headerssetqueryparameterAdd default query parametersrouterequesttoendpointRedirect request to different pathsetpropertySet body property valuespollingtriggerConfigure polling trigger behaviorupdatenextlinkFix pagination nextLink routingjson

"policyTemplateInstances": [
  {
    "templateId": "setheader",
    "title": "Set Content-Type Header",
    "parameters": {
      "x-ms-apimTemplateParameter.name": "Content-Type",
      "x-ms-apimTemplateParameter.value": "application/json",
      "x-ms-apimTemplateParameter.existsAction": "override",
      "x-ms-apimTemplateParameter.newValue": "application/json"
    }
  }
]

See POLICY_TEMPLATES.md for all templates with examples.

---

Custom Code (script.csx)#

C# code for request/response transformation when policy templates aren't sufficient.

csharp

public class Script : ScriptBase
{
    public override async Task<HttpResponseMessage> ExecuteAsync()
    {
        if (this.Context.OperationId == "MyOperation")
            return await HandleMyOperation().ConfigureAwait(false);

        // Forward all other requests unchanged
        return await this.Context.SendAsync(
            this.Context.Request, this.CancellationToken
        ).ConfigureAwait(false);
    }
}

Constraints: .NET Standard 2.0 | 2-minute timeout | 1 MB max file size | One script per connector

Common Pattern: Build Base64 Identifier from Connection Fields#

When the upstream API expects a computed identifier (for example base64("app_name:email")), collect user-friendly fields in connectionParameters and derive the required value in script.csx.

csharp

var appName = GetHeaderValue("app_name")?.Trim();
var email = GetHeaderValue("email")?.Trim();

if (!string.IsNullOrWhiteSpace(appName) && !string.IsNullOrWhiteSpace(email))
{
  var appIdentifier = Convert.ToBase64String(Encoding.UTF8.GetBytes($"{appName}:{email}"));
  // Inject into query/header as required by the API
  // Remove raw app_name/email headers before forwarding
}

Guidance:

• Use UTF-8 before Base64 encoding
• Trim values before encoding
• Remove raw source headers after deriving the computed identifier
• If accepted by the API, set both query and header forms for compatibility
• Prefer deterministic header injection via policyTemplateInstances + setheader using @connectionParameters('...'), then consume those headers in script.csx

Example apiProperties.json policy mapping:

json

"policyTemplateInstances": [
  {
    "templateId": "setheader",
    "title": "app_name",
    "parameters": {
      "x-ms-apimTemplateParameter.name": "app_name",
      "x-ms-apimTemplateParameter.value": "@connectionParameters('app_name')",
      "x-ms-apimTemplateParameter.existsAction": "override",
      "x-ms-apimTemplate-policySection": "Request"
    }
  }
]

See CUSTOM_CODE.md for full reference with examples.

---

Webhook Triggers#

Mark an operation as a webhook trigger with x-ms-trigger and define the notification payload:

json

"/hooks": {
  "x-ms-notification-content": {
    "schema": { "$ref": "#/definitions/WebhookPayload" }
  },
  "post": {
    "operationId": "WebhookTrigger",
    "summary": "When an event occurs",
    "x-ms-trigger": "single",
    "x-ms-trigger-hint": "To see it work, create a new item in the service.",
    "parameters": [
      {
        "name": "body",
        "in": "body",
        "schema": {
          "type": "object",
          "properties": {
            "callbackUrl": {
              "type": "string",
              "x-ms-notification-url": true,
              "x-ms-visibility": "internal"
            }
          }
        }
      }
    ],
    "responses": { "201": { "description": "Created" } }
  }
}

Requirements: Must also define a DELETE operation so the platform can unregister webhooks. The API must return a Location header in the 201 response pointing to the webhook resource.

See WEBHOOK_TRIGGERS.md for complete patterns.

---

Certification & Submission#

See CERTIFICATION.md for full step-by-step certification workflows, packaging instructions, and submission details for both publisher types.

Connector Requirements (Both Publisher Types)#

Connector Title:

• ≤30 characters, no restricted words ( API, Connector, Copilot Studio)
• The (Independent Publisher) suffix goes on the PR title, not the connector title in the OpenAPI definition

Connector Description: 30–500 characters, ≤1000 total, no HTML tags.

Icon (Verified Publisher only): Custom icon required — 100×100 to 230×230 px, PNG, non-white/non-default background.

OAuth: Currently unsupported for Independent Publisher certification.

Certification Process Summary#

StepIndependent PublisherVerified Publisher1Verify connector doesn't already existPrepare connector artifacts + custom icon2Submit proposal PR ( dev branch)Run Solution Checker3Build connector after approvalCreate intro.md artifact4Submit artifacts to same PRPackage solution zip + intro.md5Complete OneVet identity verificationValidate with ConnectorPackageValidator.ps16Certification review → deploy (~15 biz days, Fridays)Upload to blob (SAS URL) → submit via Partner Center (~15 biz days, Fridays)

Office Hours: Tuesdays 3:30–4:30 PM UTC with the Connector Certification Team.

PR Checklist#

• All files in correct directory ( independent-publisher-connectors/ or certified-connectors/)
• PR targets dev branch (never master)
• apiDefinition.swagger.json passes swagger validation (use Solution Checker)
• apiDefinition.swagger.json is valid JSON (no trailing/extra data) and contains no empty {} parameter/response/schema placeholders
• apiProperties.json matches schema
• readme.md / intro.md follows template (Publisher, Prerequisites, Operations, Credentials, Known Issues)
• No secrets or real API keys in any file
• Connector title is ≤30 characters, no restricted words ("API", "Connector", "Copilot Studio")
• Connector description is 30-500 characters
• Connector description is <= 1000 characters and contains no HTML tags
• Host URL is a production URL (no staging/dev/test URLs)
• Response schemas provided on success responses only (not on default response)
• All definitions.*.properties.* entries have explicit schema type/ref metadata (no ambiguous properties during OpenAPI→WADL conversion)
• x-ms-connector-metadata array present with Website, Privacy policy, Categories
• All summaries are ≤80 chars, end with alphanumeric, no slashes
• Every action/operation has a non-empty description
• All descriptions are full sentences ending in punctuation, no URLs
• Summary and description text are not identical for any operation or parameter
• All path parameters have required: true and x-ms-url-encoding: "single"
• All operationId values are PascalCase with no non-alphanumeric characters
• For OAuth connectors: "redirectMode": "GlobalPerConnector" (not "Global")
• For Independent Publisher: iconBrandColor is "#da3b01"
• For Independent Publisher with OAuth: detailed instructions for creating the OAuth app
• At least 10 successful calls per operation tested
• Screenshots of 3+ unique operations working in a Flow (Independent Publisher)
• All strings are in English, free of spelling/grammar errors
• JSON uses 4-space indentation, no trailing whitespace
• Package validated with ConnectorPackageValidator.ps1

CLI Deployment#

Two CLI tools can deploy custom connectors. Power Platform CLI ( pac) is the modern, recommended tool. paconn is the legacy Python-based tool still used in many existing guides.

Featurepac connector (Power Platform CLI)paconn (Legacy Python CLI)Installwinget install Microsoft.PowerPlatformCLI or VS Code extensionpip install paconnAuthpac auth create (interactive, service principal, device code)paconn login (device code only)Solution-awareYes — --solution-unique-name flagNoScaffoldpac connector init generates starter filesN/AList connectorspac connector listN/AValidate swaggerN/A (use ConnectorPackageValidator.ps1)paconn validate --api-def ...StatusActively maintainedMaintenance mode

Power Platform CLI ( pac connector)

bash

# Install (Windows)
winget install Microsoft.PowerPlatformCLI

# Or install via dotnet
dotnet tool install --global Microsoft.PowerApps.CLI.Tool

# Authenticate
pac auth create --environment <environment-url-or-id>

# Scaffold a new connector (generates starter apiProperties.json)
pac connector init \
  --connection-template OAuthAAD \
  --generate-script-file \
  --generate-settings-file \
  --outputDirectory MyConnector

# List connectors in current environment
pac connector list

# Create a connector
pac connector create \
  --api-definition-file apiDefinition.swagger.json \
  --api-properties-file apiProperties.json

# Create with icon, custom code, and add to a solution
pac connector create \
  --api-definition-file apiDefinition.swagger.json \
  --api-properties-file apiProperties.json \
  --icon-file icon.png \
  --script-file script.csx \
  --solution-unique-name MySolution

# Update an existing connector
pac connector update \
  --api-definition-file apiDefinition.swagger.json \
  --api-properties-file apiProperties.json \
  --connector-id <connector-id>

# If connector uses custom code, ALWAYS include script file on update
pac connector update \
  --api-definition-file apiDefinition.swagger.json \
  --api-properties-file apiProperties.json \
  --script-file script.csx \
  --connector-id <connector-id>

# Download a connector's files
pac connector download \
  --connector-id <connector-id> \
  --outputDirectory ./MyConnector

paconn CLI (Legacy)

bash

# Install the CLI
pip install paconn

# Authenticate
paconn login

# Create a connector
paconn create --api-def apiDefinition.swagger.json --api-prop apiProperties.json

# With custom code and icon
paconn create --api-def apiDefinition.swagger.json --api-prop apiProperties.json \
  --script script.csx --icon icon.png

# Update an existing connector
paconn update --api-def apiDefinition.swagger.json --api-prop apiProperties.json \
  --connector-id <connector-id>

# Validate swagger definition
paconn validate --api-def apiDefinition.swagger.json

# Download connector files
paconn download -e <environment-id> -c <connector-id>

Tip: Both CLIs support a settings.json file to store environment, connector ID, and file paths — avoiding repetitive flags on every command. When using paconn, always download first as a backup before running update.

Reliability note: pac connector update with --script-file can intermittently fail with CustomScriptProvisioningFailed (often surfaced as upstream 502). This is commonly transient; retry the same command after a short delay before changing connector files.

README Template#

markdown

# Service Name
Short description of the service (2-3 sentences).

## Publisher: Your Name

## Prerequisites
- An account with [Service Name](https://service.com)
- An API key (obtained from Settings > API Keys)

## Supported Operations
### List Items
Retrieves all items from your account.

### Create Item
Creates a new item with the specified properties.

## Obtaining Credentials
Step-by-step instructions for getting API credentials.

## Known Issues and Limitations
- Rate limited to 100 requests per minute
- Maximum 1000 items per response

## Deployment Instructions
Run one of the following commands:
\`pac connector create --api-definition-file apiDefinition.swagger.json --api-properties-file apiProperties.json\`
or (legacy):
\`paconn create --api-def apiDefinition.swagger.json --api-prop apiProperties.json\`

---

Pagination Support#

For connectors to leverage Power Platform's built-in paging, the API must return responses following this pattern:

json

{
  "nextLink": "https://api.example.com/items?page=2",
  "value": [
    { "id": "1", "name": "Item 1" },
    { "id": "2", "name": "Item 2" }
  ]
}

Requirements:

• value — Array of result items (required on every page)
• nextLink — Full URI to the next page (present only when more pages exist; omit on the final page)
• Return HTTP 200 for all paginated responses

When the last page is reached, omit nextLink entirely — Power Platform stops paging automatically.

Important runtime caveat (custom code):

• Do not rely on script.csx to reshape pagination payloads for built-in auto paging.
• In practice, follow-up requests triggered internally by platform auto-pagination may bypass custom response transformation logic.
• If page 1 is transformed to include value/ nextLink but the upstream API returns a different shape on subsequent pages (for example data/ next), built-in pagination can still fail.

Recommended approach:

• Prefer native upstream pagination contracts for built-in paging ( value + nextLink on every page).
• If upstream payloads are non-standard and cannot be changed, implement manual pagination in the flow (Do Until) or create a dedicated custom action that fetches/aggregates pages explicitly.

Pagination decision tree (use this before implementing):

1. Can the upstream API return value + nextLink on every page?

• Yes → Use built-in connector pagination.
• No → Continue to step 2.

1. Can updatenextlink policy safely map the API's paging model?

• Yes → Use updatenextlink + built-in pagination.
• No → Continue to step 3.

1. Need all records in a single action output?

• Yes → Build a dedicated custom "fetch all pages" action.
• No → Use manual pagination in Flow ( Do Until) and process page-by-page.

Rule of thumb: If pagination correctness depends on response reshaping in script.csx, do not use built-in auto-pagination as the primary design.

If the API uses non-standard pagination (e.g., page/ limit query parameters, cursor-based, or offset-based), you have two options:

1. Use the updatenextlink policy template to rewrite the pagination URL into the nextLink format Power Platform expects
2. Build pagination logic in a Power Automate flow using a Do Until loop that increments the page parameter until no more results are returned

Add limit and page parameters to operations that support pagination:

json

{
  "name": "limit",
  "in": "query",
  "type": "integer",
  "required": false,
  "x-ms-summary": "Page Size",
  "description": "The number of items to return per page."
},
{
  "name": "page",
  "in": "query",
  "type": "integer",
  "required": false,
  "x-ms-summary": "Page Number",
  "description": "The page number of results to retrieve."
}

---

Using AI to Accelerate Development#

Leverage AI assistants to generate boilerplate OpenAPI extensions and documentation. This is especially valuable when an API has many operations or parameters that each need x-ms-summary, description, and title attributes.

Generating OpenAPI extensions prompt:

Acting as a Power Platform developer, I would like your assistance in writing a custom connector. I will provide each path for the API. Include the following:

• A summary and description attribute for each path
• A description and x-ms-summary attribute for each path parameter and response property; the x-ms-summary should read like a title for the name field
• A title, description, and x-ms-summary attribute for each response property; the title and x-ms-summary will be the same
• If the name attribute is used in the description, then update the description to use the new title attribute

Please update the file with those additional attributes and provide it back to me. Here is the first path:

json

<paste path here>

Generating README prompt:

Acting as a technical writer, create a README.MD file for the custom connector. Below is the template — do not deviate from it. When generating the operations, include all input attributes and use the friendly names.

TEMPLATE:

text

# {Connector Title}
{Description from the OpenAPI info.description}

## Publisher: {Your Name}

## Prerequisites
{How to get an account and API credentials}

## Supported Operations
### {Operation Summary}
{Operation description}
- **Inputs:** `{Param x-ms-summary}`: {param description}
- **Outputs:** `{Property title}`: {property description}

## Obtaining Credentials
{Step-by-step instructions}

## Known Issues and Limitations
{Current limitations or "Currently, no known issues or limitations exist."}

OPENAPI FILE:

json

<paste full apiDefinition.swagger.json>

Tips:

• Process paths individually for APIs with many operations — large files may exceed context limits
• Always review and validate AI output against the coding standards before submission
• AI works best when the source API has comprehensive documentation

---

Testing and Debugging#

After importing the connector into Power Platform via the Custom Connector Wizard or CLI:

1. Test every operation in the connector's Test tab — run at least 10 successful calls per operation
2. Use the Swagger Editor toggle in the custom connector editor for quick inline edits to fix validation errors
3. Common schema validation fixes:
   • Remove required arrays from response schemas — if the API doesn't always return every field, the required constraint causes validation failures. Keep required on request body schemas but remove from response schemas
   • Fix type mismatches — if the API returns a string where the schema says integer (or vice versa), update the schema to match actual API behavior
   • Remove empty schema properties — empty properties: {} on responses can cause issues
4. Re-test after every change — iterate until all operations pass cleanly
5. Create test flows in Power Automate using 3+ unique operations to verify end-to-end behavior and capture screenshots for PR submission

Post-Deploy Verification (Recommended)#

After pac connector create or pac connector update:

1. Download the deployed connector files using pac connector download --connector-id <id>
2. Perform semantic JSON comparison between local and downloaded files
3. Focus on functional parity for:

• OpenAPI paths/parameters/responses
• x-ms-dynamic-values mappings
• connectionParameters and script wiring

1. Treat these as common platform-managed non-functional differences unless behavior changed:

• policyTemplateInstances may be auto-added
• publisher or stackOwner may differ/appear blank in downloaded apiProperties.json

---

Best Practices#

Do:

• Use x-ms-summary on every parameter and schema property (controls designer labels)
• Use x-ms-visibility: "internal" for parameters with fixed values (e.g., api-version)
• Provide default values for all internal required parameters
• Include complete response schemas on success responses only (enables dynamic content in flows)
• Use $ref definitions and $ref parameters for reusable schemas and shared parameters
• Test with the custom connector wizard before submitting PR — run at least 10 successful calls per operation
• Run Solution Checker and ConnectorPackageValidator.ps1 before submitting
• Use policy templates before reaching for custom code
• Use PascalCase for operationId — remove all non-alpha characters
• Keep summary to 80 characters or fewer, sentence case, ending with an alphanumeric character
• Ensure summaries contain only alphanumeric characters or parentheses — no slashes
• Start summaries with "List" (returns many) or "Get" (returns one); for triggers: "When a [event]"
• Make sure summary and description have different text on every operation/parameter
• Write description as full sentences ending in punctuation — no URLs
• Keep parameter helper text concise for designer UX; avoid repetitive boilerplate and long non-clickable references
• Add title (Title Case) and description (full sentence) to all definition properties (skip for $ref)
• Add "x-ms-url-encoding": "single" and "required": true to all path parameters
• Add minimum/ maximum when number/integer ranges are known
• Use type: "boolean" for true/false inputs instead of string flags
• For nullable response primitives, use x-nullable: true and remove from required when null/omitted is possible
• Ensure all text is in English and free of grammatical/spelling errors
• Capitalize abbreviations to avoid translation issues
• Use "redirectMode": "GlobalPerConnector" for all OAuth connectors
• Use 4-space soft tabs and remove trailing whitespace in JSON files
• Use only production host URLs (no staging, dev, or test URLs)
• Explicitly set consumes and produces to ["application/json"] — don't rely on defaults
• Back up connector files using source control before running update commands
• For APIs with multiple cloud endpoints (e.g., commercial, GCC, GCC High, DoD), use the dynamichosturl policy template to let users select the correct endpoint at connection time

Don't:

• Use OpenAPI 3.0 — must be Swagger 2.0
• Include real API keys or secrets in files (use dummy values: <<Enter your API key>>)
• Submit PR to master branch (always target dev)
• Leave x-ms-connector-metadata empty or missing
• Use wrong brand color for Independent Publisher (must be #da3b01)
• Skip response schemas (breaks dynamic content in Power Automate)
• Put schemas on the default response — schemas belong on explicit success responses (200/201) only
• Exceed 1 MB for the OpenAPI definition file
• Put schemas on error responses (4xx/5xx) — descriptions only
• Leave default values on definition properties (only on operation parameters)
• Include empty properties unless they are required
• Put URLs in title or description fields
• Name any parameter connectionId (reserved by the platform)
• Include body or form data parameters on GET operations
• Use "redirectMode": "Global" — must be "GlobalPerConnector" (mandatory since Feb 2024)
• Exceed 30 characters for connector title
• Include required arrays on response schemas — they cause validation failures when the API omits optional fields
• Use OpenAPI 3 nullable union syntax in Swagger 2.0 files (for example "type": ["integer", "null"])

Known limitation: When using paconn, the stackOwner property in apiProperties.json prevents paconn update from working. Workaround: maintain two versions of your apiProperties — one with stackOwner for certification submission and one without for local environment updates via paconn. The pac connector CLI does not have this limitation.

See COMMON_MISTAKES.md for a full error catalog with fixes.

---

Session Learnings#

Use this section as a lightweight changelog for practical field learnings that should influence future connector work.

2026-02-18: HDX Connector Session#

• Swagger 2.0 strictness: Non-body parameters without type caused APIM import failures ( JSON is valid against no schemas from 'oneOf'); adding explicit type resolved deployment.
• Metadata-driven UX: Mapping metadata endpoints to x-ms-dynamic-values significantly improved usability by enabling dropdowns for common filter parameters.
• Computed auth pattern: Collecting app_name + email as connection parameters and computing app_identifier in script.csx (UTF-8 Base64) produced a cleaner auth experience.
• Deterministic parameter flow: For custom code that reads connection values from headers, explicitly map with policyTemplateInstances + setheader ( @connectionParameters('app_name'), @connectionParameters('email')) instead of relying on implicit runtime behavior.
• Input normalization: Trimming connection values before encoding prevented malformed identifiers from accidental whitespace.
• Operational reliability: pac connector update with custom code can intermittently fail with CustomScriptProvisioningFailed/502; retrying the same command after a short delay often succeeds.
• Deployment discipline: When a connector has script.csx, include --script-file script.csx on every pac connector update; otherwise code changes might not be published with schema updates.
• Verification approach: Post-deploy semantic comparison is more reliable than byte-for-byte diff because downloaded files may include platform-managed differences.
• WADL hardening: In addition to property typing, Power Apps WADL conversion also requires typed array items and rejects readOnly properties in required arrays.

2026-02-25: HDX Connector UX & Nullability Session#

• Input description UX: Power Automate surfaces parameter description as helper text; concise descriptions materially improve usability. Prefer short guidance over repeated phrases like "Filter the response by...".
• No dead links in helper text: URLs/HTML anchors in parameter descriptions are not useful in designer helper text; remove them from input descriptions.
• Enum helper strategy: For short enums, include values inline ( Allowed values: ...). For long enums shown as dropdowns, use concise text such as "Select from dropdown.".
• Boolean correctness: Converted boolean-like query flags ( has_hrp, in_gho, origin_*, asylum_*, is_hxl) from string to boolean to align schema with runtime semantics.
• Swagger 2.0 nullable safety: Avoid type arrays (for example ["integer", "null"]) because they can pass some validators but fail connector import/parsing; use x-nullable: true with scalar type instead.
• Required vs nullable: If upstream API returns null or omits fields, remove those fields from response required arrays rather than coercing values (for example, avoid null→0 data mutation unless explicitly desired).

2026-02-26: HDX Auto-Pagination Session#

• Auto-pagination + custom code caveat: Built-in platform auto-pagination may execute follow-up page calls outside custom script.csx response-shaping assumptions.
• Design implication: Do not depend on custom code to retrofit page 2+ into value/ nextLink for built-in pagination.
• Preferred fallback: Use manual pagination (Do Until) or a dedicated "fetch all pages" action when the upstream API cannot natively emit Power Platform paging shape on every page.

---

Troubleshooting#

SymptomLikely CauseFixJSON is valid against no schemas from 'oneOf'Non-body parameter missing typeAdd type: "string" (or appropriate type) to every query/header/path/formData parameterDefaultResponseHasSchemaSchema on default responseMove schema to the 200/ 201 response; remove schema from default``CustomScriptProvisioningFailed / 502Transient deployment errorRetry the same pac connector update command after a short delayDynamic content missing in Power AutomateNo response schema on success responseAdd a complete schema to the 200 responsePathParameterMustBeRequiredPath parameter missing required: trueAdd "required": true and "x-ms-url-encoding": "single"``ConnectionIdParameterNotAllowedParameter named connectionIdRename the parameter (e.g., connId)The 'collectionFormat' value 'Multi' is not supportedArray parameter with collectionFormat: "multi"Change to type: "string", accept comma-separated values, split in script.csx``An error occured while converting OpenAPI file to WADL fileAmbiguous definition properties (missing type/ $ref)Ensure every definitions.*.properties.* has an explicit schema discriminatorProperties show raw technical names in designerMissing x-ms-summary or titleAdd x-ms-summary to parameters; add title and description to definition propertiesDouble-encoded path parametersMissing x-ms-url-encodingAdd "x-ms-url-encoding": "single" to all path parametersOAuth connector certification rejectedUsing redirectMode: "Global"Change to "redirectMode": "GlobalPerConnector"Connector title rejectedTitle > 30 chars or contains "API"/"Connector"Shorten title and remove restricted words

For the full error catalog with detailed fixes and code examples, see COMMON_MISTAKES.md.

---

Related Files#

• OPENAPI_EXTENSIONS.md — Detailed reference for all x-ms-* extensions with examples
• AUTH_PATTERNS.md — API Key, OAuth 2.0 (AAD/Generic), Basic Auth, and Multi-Auth patterns
• POLICY_TEMPLATES.md — All policy template IDs with configuration examples
• CUSTOM_CODE.md — C# script.csx patterns, ScriptBase class, supported namespaces
• WEBHOOK_TRIGGERS.md — Webhook trigger registration, notification, and deletion patterns
• CERTIFICATION.md — Full certification workflows for Independent and Verified Publishers, packaging, and submission
• EXAMPLES.md — Complete working connector examples for common scenarios
• COMMON_MISTAKES.md — Error catalog with fixes and validation tips