Context7 — look up current library documentation

Context7 fetches current documentation for a library, framework, SDK, or CLI from the Upstash Context7 index, so an agent works from the API as it exists now instead of from memory. It covers signatures, config fields, and setup steps.

Two access paths read the same index: the ctx7 CLI for a one-off lookup, and the @upstash/context7-mcp MCP server when the agent should call the tools itself via resolve-library-id and query-docs. The CLI needs Node.js 22.13+; the MCP package needs Node.js 20.18.1+.

Lookup is two steps: resolve a library name to an id, then query that id with one topic per query. --json gives output an agent can parse, and --language ranks examples in a given language first. Calls work without an API key; a key from the Context7 dashboard raises the rate limit.

Queries go to Context7, so keep private code, keys, and passwords out of them. When several libraries share a name, prefer the id whose name matches with more snippets and a higher reputation score, and note that an old id can redirect to a current one.