Context7 MCP Server — Real-Time Library Docs for AI Coding Agents

At a glance: 50.1K stars, 2.4K forks, 148 open issues, MCP server v2.1.4, CLI ctx7 v0.3.6, ~10.1M estimated PulseMCP visitors Context7 is the most popular MCP server in 2026. Built by Upstash , it solves a genuine pain point: AI coding assistants hallucinate APIs that don't exist because their training data is months or years out of date. When your agent needs to use a library, Context7 fetches the current, version-specific documentation and injects it directly into the prompt. No tab-switching, no copy-pasting, no outdated code generation. But popularity doesn't mean perfection. A critical context poisoning vulnerability (ContextCrush) was discovered and patched in February 2026. The free tier was cut by 83–92% in January 2026. And the centralized registry model creates a trust surface most developers haven't thought through. What It Does Two MCP tools: resolve-library-id — look up a library in Context7's registry query-docs — fetch version-specific documentation for a topic That's it