Using Context7

What this is

Context7 is an MCP server that fetches current documentation for libraries, frameworks, and SDKs on demand. Your training data is months-to-years stale; Context7 is the corrective.

When to use

Use whenever the user asks about:

• A library's API, configuration, or setup (React, Next.js, Django, Prisma, Tailwind, Express, Spring, FastAPI, LangChain, ...)
• Version-specific behavior or migration (Next.js 14 → 15, React 18 → 19)
• "How do I do X with Y" where Y is any named library/framework
• Best practices or recommended patterns for a specific tool
• Configuration files (tailwind.config.js, next.config.ts, prisma.schema)

Even if you "feel like you know" the answer — query Context7 first. Library APIs churn fast: server actions, app router, RSC, Tailwind v4, Prisma 6 migrations all shipped after most training cutoffs. Confidence-from-memory is the failure mode.

When NOT to use

• Refactoring existing code (the code itself is the spec)
• Writing PowerShell/Bash scripts (general shell knowledge)
• Debugging business logic (no library API involved)
• Code review for style/correctness
• Generic programming concepts (sorting algorithms, OOP patterns, recursion)
• Internal company code (Context7 only knows public libraries)

Workflow

Two-call pattern, always in this order:

Step 1: Resolve library ID

mcp__context7__resolve-library-id
  libraryName: "Next.js"           # official name with punctuation
  query: "How to set up server actions in Next.js 15"

Returns one or more matches in the form /org/project or /org/project/version. Pick the highest-reputation, highest-snippet-count match. If the user named a version (React 19, Next.js 14.3), prefer the versioned ID like /vercel/next.js/v14.3.0-canary.87.

Skip step 1 only when the user already gave you the ID in /org/project form (rare).

Step 2: Query docs

mcp__context7__query-docs
  libraryId: "/vercel/next.js"
  query: "How to set up server actions with form validation in Next.js 15"

The query goes to the Context7 API. Be specific.

Query writing — good vs bad

Good queries (specific intent, named feature, target version):

• "How to set up JWT authentication middleware in Express.js"
• "Prisma schema for a one-to-many relation with cascade delete"
• "React 19 useFormStatus hook example with form submission"
• "Tailwind v4 custom theme tokens with CSS variables"
• "FastAPI dependency injection for database session lifecycle"

Bad queries (vague, single-word, intent unclear):

• "auth"
• "hooks"
• "react"
• "config"
• "best practices"

If your query is one word or one short noun phrase, rewrite it before sending.

Constraints

• Maximum 3 calls per question to Context7. If you can't find what you need after 3 calls, work with what you have.
• Don't pass secrets, API keys, customer data, or proprietary code in the query field — it leaves your machine.
• The libraryName field on resolve-library-id should be the official spelling: Next.js not nextjs, Three.js not threejs, Customer.io not customerio.

Red flags — stop and use Context7

• User asks "how do I do X in [framework] [version]" and you start typing from memory
• You're about to give a CLI command (npx create-..., pnpm add ...) without checking
• You're explaining a config file format from memory
• You catch yourself thinking "I'm pretty sure it's useFormStatus..." — verify it
• You're migrating code between two versions and reasoning about the diff from memory

Anti-pattern: skipping resolution

Do not invent a library ID and call query-docs directly. The resolution step is what guarantees you hit the right project (there are many react-* packages) and the right version. Skipping it leads to docs for the wrong library.

Combining with other tools

• Followed by Write/Edit: query Context7, then write code informed by current API
• With deepwiki: use Context7 for how to use a library, deepwiki for how a repo is built internally
• With sequential-thinking: when designing an architecture that spans multiple libraries, query each, then reason

One-liner reminder

If a library name appears in the user's question and you haven't queried Context7 yet, you're about to ship stale information.