Context7

Sweet spot: any developer using an MCP-capable AI coding assistant in 2026. The cost-to-install is sub-five-minutes and the upside (fewer wrong-API moments per day) is immediate. This is the kind of small tool that quietly changes your daily experience. Failure modes. If you are building against an internal library, a private API, or a pre-release version not in the index, Context7 cannot help you — you still need to paste docs into the chat. The assistant also needs to actually use the MCP tool; if your system prompt does not encourage that, the model may still guess. What to pilot. Install it in Cursor or Claude Code, then ask three questions about a library that has had a major version bump in the last six months (e.g., Tailwind 4, Next 15). Compare answers with and without Context7. The difference is usually obvious within five prompts.

Context7 is a Model Context Protocol (MCP) server from Upstash that solves a specific, painful problem: AI coding assistants hallucinate APIs because their training data is months out of date. When you ask Claude, Cursor, Windsurf, or VS Code Copilot about a library, you often get code that references deprecated methods or APIs that never existed in that version. Context7 maintains a searchable, version-aware index of current documentation for thousands of libraries (React, Next.js, Prisma, FastAPI, Supabase, etc). Via the MCP protocol, the assistant can fetch the exact current docs for the version you specify and ground its answer in them. No stale API hallucinations, no fighting deprecations from last year. It ships as a free hosted MCP endpoint for individual developers and an npm package for CLI use. The core is open-source; Upstash hosts the index and keeps it fresh. Added to Cursor / Claude Code / Windsurf by pointing the MCP client at context7.com — a one-line config change.