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 rollout acceptance is still pending.

Web Fetch

Fetch and analyze content from one or more URLs using Gemini 2.5 Flash with URL context.

nansen web fetch https://nansen.ai --question "What products does Nansen offer?"
nansen web fetch --url https://example.com --url https://other.com --question "Compare these two sites"
nansen web fetch https://docs.uniswap.org/contracts/v4/overview --question "What changed in v4?"

Positional args and --url flags can be combined — all become URLs to fetch.