Authentication#

Nansen account API calls accept a selected nansen:api browser session or conventional API key with the same permissions. NANSEN_API_KEY takes precedence; optional primaryEnv preserves configured-key injection. Run nansen auth status for offline selection. Cached access expiry alone permits automatic renewal during an authorized task. Stop on anonymous selection, invalid state, blocked/uncertain renewal or actual auth failure; never drop a credential or fall back to anonymous x402 payment. Browser login does not grant wallet signing, privileged service identity or a persistent MCP integration key. Preserve all confirmation, signing, sanctions and geographic checks below. Browser login is available in CLI 2.0.0 within the macOS arm64 preview scope.

Agent vs CLI Routing#

Public agent fast/expert and direct API commands accept the selected nansen:api browser session or conventional API key under the same account permissions.

Need a...Usetake (analysis, interpretation)nansen agenttable (raw data, specific metrics)Direct CLI commandsreport (both)Agent for narrative + CLI for data

Use nansen agent when#

• Question requires interpretation or synthesis across multiple data sources
• Open-ended research: "analyse this wallet", "what's happening with ETH smart money?"

bash

nansen agent "What are top smart money tokens on Solana today and why?"
nansen agent "Analyse wallet 0x123... -- is this a smart trader?"
nansen agent "..." --expert   # deeper analysis, 750 credits

Cost: 200 credits (fast) / 750 credits (expert)

Use direct CLI commands when#

• You need specific structured data -- prices, volumes, holders, flows
• Deterministic question: "top 10 tokens by netflow on ethereum"
• Piping output or building a data table

bash

nansen research token screener --chain ethereum --smart-money --limit 10
nansen research smart-money netflow --chain solana
nansen research profiler balance --address 0x123... --chain ethereum

Cost: 5-50 credits per call

Anti-patterns#

• Don't use nansen agent for simple data fetches -- 40x more expensive
• Don't use raw CLI for open-ended analysis -- returns data, not interpretation
• Don't chain 3+ agent calls -- get raw data via CLI, call agent once for synthesis

Browser session scope#

Plain nansen login requests fresh browser approval; --no-browser prints the link/code for approval on another device and keeps the same native-storage requirements. NANSEN_API_KEY overrides the single saved credential. Use nansen auth status for offline cached/unverified selection details and nansen account for a free live check. Explicit login --human or login --api-key retains legacy key setup. Selected browser sessions renew automatically; uncertain renewal requires fresh login without replay or fallback to another account/payment.

Browser nansen:api grants have API-key-equivalent account permissions, subject to enabled admission and the same endpoint restrictions. Internal service identity and wallet signing are not granted. Browser sessions cannot authorize wallet signing or be exported as MCP keys. CLI 2.0.0 is published; the preview platform limits above still apply.