AgentLine — AI Telephony Skill#

Give your AI agent a real phone number and voice calls — no servers, no webhooks, no infrastructure.

First-Time Setup#

Follow these steps IN ORDER when setting up AgentLine for the first time:

1. Check for AGENTLINE_API_KEY (starts with sk_live_) — this is required.

   • If you do NOT have this key, stop and ask the human to sign up or log in at https://agentline.cloud to get their API key. Do NOT proceed without it.

2. Check for AGENTLINE_AGENT_ID (starts with agt_) — this is optional.

   • If you already have one, use it and skip to step 3.
   • If you do NOT have one, create a new agent now by calling POST /v1/agents with {"name": "My Agent"}. Save the returned agent ID.

3. Ask for area code and provision the number — Always ask the human:

   "What area code would you like for your phone number? (e.g. 212 for NYC, 415 for SF, 313 for Detroit)"

   • Once they give an area code, call POST /v1/numbers with {"agent_id": "...", "area_code": "XXX"}
   • If it succeeds, confirm the provisioned number to the human
   • If it fails (no numbers available for that area code), tell them and ask for a different area code

4. Ask for voice preference — Always ask the human:

   "Would you like your agent to have a male or female voice?"

   • If female: set voice_id to "female-1" (or "female-2" for warmer tone)
   • If male: set voice_id to "male-1"
   • Apply via PATCH /v1/agents/$AGENTLINE_AGENT_ID with {"voice_id": "chosen_preset"}
   • Available presets: female-1, female-2, male-1 — or any Cartesia voice UUID

5. Start the background event poller — This is MANDATORY. Write the polling script (see Events Mailbox section below) to a scratch file and launch it as a background command. Without this, you will miss all inbound calls and SMS messages.

⚠️ Do NOT skip ANY steps. Steps 1-4 set up the agent. Step 5 keeps it alive and aware of incoming calls/texts.

• Write the polling script (Bash for Linux/macOS, PowerShell for Windows) from the Events Mailbox section below
• Launch it as a background process with terminal(background=true)
• Verify it's running

⚠️ Do NOT skip steps or change the order. The human should have a working agent with their chosen area code number, voice, and running event poller by the end.

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Authentication#

Every request: Authorization: Bearer $AGENTLINE_API_KEY + Content-Type: application/json

Base URL: https://api.agentline.cloud

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How Calls Work (Hosted Mode)#

AgentLine runs in Hosted Mode — the server runs the AI voice conversation autonomously. You create a call, the AI handles it, you retrieve the transcript afterwards.

System Prompts#

• Dynamic prompt — system_prompt field in POST /v1/calls. Overrides default for that call only.
• Default prompt — stored on agent via PATCH /v1/agents/{agent_id}. Used for all inbound calls and outbound calls without a dynamic prompt.

⚠️ system_prompt is a FULL REPLACE, not append. The voice AI has no memory between calls — put everything (personality, instructions, current context) in the prompt. Update it whenever your context changes.

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Make an Outbound Call#

bash

curl -X POST $AGENTLINE_URL/v1/calls \
  -H "Authorization: Bearer $AGENTLINE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"agent_id": "$AGENTLINE_AGENT_ID", "to_number": "+1XXXXXXXXXX", "system_prompt": "...", "initial_greeting": "...", "voice_id": "female-1"}'

FieldRequiredDescriptionagent_idYesYour agent IDto_numberYesE.164 phone number to callsystem_promptNoDynamic prompt for this call only (overrides default)initial_greetingNoWhat the agent says first when the person picks upvoice_idNo"female-1", "female-2", "male-1", or Cartesia UUID

After every outbound call: Poll GET /v1/calls/<call_id> every ~10s until status=completed, then GET /v1/calls/<call_id>/transcript. Summarize and share with human. Never consider a call "done" without the transcript.

If you get 400 "Agent has no active phone number", provision one first.

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End a Call#

POST /v1/calls/<call_id>/hangup

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Get Call Transcript#

GET /v1/calls/<call_id>/transcript — Returns [{role, text, timestamp}, ...]

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Events Mailbox#

Events are pushed when someone calls or texts your agent's number. You MUST poll regularly.

Event types: call.received (inbound call started), call.completed (call ended, includes transcript), sms.received (inbound SMS)

⚡ MANDATORY — Background Event Polling#

⚠️ Do NOT use schedule/cron to poll. Use the background script approach — it only wakes you when events exist.

Setup: Write the polling script to a scratch file, then launch as a background command with WaitMsBeforeAsync=500.

Windows (PowerShell):

powershell

param([string]$ApiKey, [string]$BaseUrl = "https://api.agentline.cloud", [int]$Interval = 50)
$headers = @{ "Authorization" = "Bearer $ApiKey" }
while ($true) {
    try {
        $r = Invoke-RestMethod -Uri "$BaseUrl/v1/events/peek" -Headers $headers -Method Get -ErrorAction Stop
        if ($r.count -gt 0) { Write-Output "AGENTLINE_EVENTS_FOUND: $($r.count) pending event(s). Call GET /v1/events to consume." }
    } catch {
        if ($_.Exception.Response.StatusCode -eq 401) { Write-Output "AGENTLINE_AUTH_ERROR"; break }
    }
    Start-Sleep -Seconds $Interval
}

macOS/Linux (Bash):

bash

#!/usr/bin/env bash
set -uo pipefail
API_KEY="$1"; BASE_URL="${2:-https://api.agentline.cloud}"; INTERVAL="${3:-50}"
while true; do
  RESP=$(curl -s -w "\n%{http_code}" "$BASE_URL/v1/events/peek" -H "Authorization: Bearer $API_KEY" 2>/dev/null) || { sleep "$INTERVAL"; continue; }
  CODE=$(echo "$RESP" | tail -1); BODY=$(echo "$RESP" | sed '$d')
  [ "$CODE" = "401" ] && { echo "AGENTLINE_AUTH_ERROR"; exit 1; }
  [[ "$CODE" != 2* ]] && { sleep "$INTERVAL"; continue; }
  COUNT=$(echo "$BODY" | grep -oP '"count"\s*:\s*\K[0-9]+' 2>/dev/null || echo "0")
  [ "$COUNT" -gt 0 ] && echo "AGENTLINE_EVENTS_FOUND: $COUNT pending event(s). Call GET /v1/events to consume."
  sleep "$INTERVAL"
done

When notified with AGENTLINE_EVENTS_FOUND: Call GET /v1/events to consume, process each event, report to human.

Endpoints#

• Consume events: GET /v1/events — returns events oldest-first, auto-deleted after retrieval
• Peek (don't consume): GET /v1/events/peek
• Filter: ?agent_id=agt_xxx or ?event_type=call.completed or ?event_type=sms.received

Event payload structure#

Each event contains: event_id, agent_id, event_type, and a payload with call/SMS details. call.completed payloads include from_number, to_number, duration_seconds, and full transcript array. sms.received payloads include from_number, body, and media_url.

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List Calls#

GET /v1/calls?limit=20 or GET /v1/calls?status=completed&limit=10

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Get Call Details#

GET /v1/calls/<call_id>

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SMS#

⚠️ SMS sending is NOT enabled. Do NOT attempt outbound SMS/MMS.

Inbound SMS arrives as sms.received events in the Events Mailbox. View message history: GET /v1/messages?limit=20

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Update Agent (System Prompt, Voice, etc.)#

PATCH /v1/agents/$AGENTLINE_AGENT_ID with any of:

FieldDescriptionsystem_promptFull instructions + current context for voice AIinitial_greetingWhat the agent says when answering inbound callsnameDisplay namevoice_id``"female-1", "female-2", "male-1", or Cartesia UUIDmodel_tier``"turbo", "balanced", or "max"

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Get/List Agents#

• Get one: GET /v1/agents/$AGENTLINE_AGENT_ID
• List all: GET /v1/agents

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Voice Settings#

Priority (highest wins): per-call → per-agent → per-account

• List voices: GET /v1/voices
• Set account default: PATCH /v1/account/voice with {"voice_id": "female-1"}
• Check current: GET /v1/account/voice
• Reset to default: DELETE /v1/account/voice

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Phone Numbers#

Each agent needs one phone number. Only US numbers supported. $2.00 per number.

Provision (Buy) a Number#

POST /v1/numbers with:

FieldRequiredDescriptionagent_idYesAgent to attach tocountryYesMust be "US"``area_codeNoPreferred 3-digit area code (e.g. "212", "313"). Always ask the user!number_typeNo"local" or "tollfree" (default: local)

If no numbers are available for the requested area code, the API returns an error — ask the user for a different area code.

List Numbers#

GET /v1/numbers

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Billing#

• Check balance: GET /v1/billing/balance
• Expenditure: GET /v1/billing/expenditure?period=current_month (also: last_month, all_time, YYYY-MM)
• Call charges: GET /v1/billing/expenditure/calls?limit=10
• Number charges: GET /v1/billing/expenditure/numbers
• Verify charge: GET /v1/billing/verify/<call_id>

Rates#

ItemCostCalls (in/out)$0.10/min (billed per second)Phone number$2.00 (one-time)

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Rules#

1. E.164 format — always +1XXXXXXXXXX for US numbers.
2. Confirm before calling — never auto-dial without explicit consent.
3. No outbound SMS — inform user it's not available if they ask.
4. Keep voice responses short — under 30 words per turn.
5. US only — country must be "US".
6. Don't release numbers — numbers are permanent once provisioned.
7. Always retrieve transcripts — poll until completed, fetch transcript, summarize for human.
8. Always check events — poll GET /v1/events for inbound calls and SMS. Proactively check at conversation start.
9. Voice changes take effect on next call — update immediately when asked.