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.

Web Fetch#

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

bash

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.

FlagValuesDefaultPurpose--urlURL—URL to fetch (repeatable for multiple URLs, up to 20)--questionstringrequiredQuestion to answer about the URL content--prettyflagoffHuman-readable JSON

Returns:

• analysis — AI-generated answer to your question
• retrieved_urls — URLs successfully fetched
• failed_urls — URLs that could not be retrieved

Tip: Combine with web search — search first to find relevant URLs, then fetch to get full content.

bash

# Find and analyze in two steps
nansen web search "uniswap v4 launch" --num-results 3 --fields link
nansen web fetch https://blog.uniswap.org/... --question "What are the key changes?"

Note: 30s timeout. Paywalled or bot-blocked pages may appear in failed_urls.