150 lines
4.9 KiB
Markdown
150 lines
4.9 KiB
Markdown
---
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name: context7-lookup
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description: Retrieve up-to-date, version-specific documentation for libraries and frameworks using Context7 MCP server. Eliminates hallucinated APIs and outdated code examples.
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---
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# Context7 Documentation Lookup
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Fetches current documentation for 68,000+ libraries to prevent hallucinated APIs and outdated code examples.
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## When to Use
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Auto-invoke when encountering:
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- Import/require/use statements for external packages (any language)
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- Error messages mentioning library names
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- User specifies library: "use {library}", "implement with {framework}"
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- Planning with third-party dependencies
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- Dependency files present (package.json, requirements.txt, Cargo.toml, pom.xml, Gemfile, go.mod, composer.json, *.csproj, etc.)
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## Protocol
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**Step 1: Detect Version** (if library known)
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```bash
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grep_search(query="{library}", includePattern="**/package.json") # Node.js
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grep_search(query="{library}", includePattern="**/requirements.txt") # Python
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grep_search(query="{library}", includePattern="**/Cargo.toml") # Rust
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grep_search(query="{library}", includePattern="**/pom.xml") # Java
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grep_search(query="{library}", includePattern="**/Gemfile") # Ruby
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grep_search(query="{library}", includePattern="**/go.mod") # Go
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grep_search(query="{library}", includePattern="**/composer.json") # PHP
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```
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**Step 2: Resolve Library ID**
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```
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mcp_context7_resolve-library-id(
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libraryName: "{library}",
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query: "{specific_use_case}"
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)
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→ Returns: /owner/repo or /domain
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```
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**Step 3: Fetch Documentation**
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```
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mcp_context7_query-docs(
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libraryId: "{resolved_id}",
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query: "{library} {version} {specific_api_or_pattern}"
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)
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→ Returns: Documentation snippets with code examples
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```
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**Step 4: Apply & Cache**
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- Use verified API signatures in implementation
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- Update FINDINGS.md with: library, version, Context7 ID, date, key patterns
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## Version Detection
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| Ecosystem | Files | Extract From |
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|-----------|-------|--------------|
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| Node.js | package.json, *lock.yaml | `dependencies` / `devDependencies` |
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| Python | requirements.txt, Pipfile, pyproject.toml | Version specifiers (==, >=, ~=) |
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| Java | pom.xml, build.gradle* | `<version>` / version strings |
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| Rust | Cargo.toml | `[dependencies]` |
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| Ruby | Gemfile* | Gem versions |
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| Go | go.mod | Module versions |
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| PHP | composer.json | `require` |
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| C#/.NET | *.csproj, packages.config | PackageReference |
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| Swift | Package.swift, Podfile | Dependencies |
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## Library Extraction from Imports
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| Language | Import | Extract |
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|----------|--------|---------|
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| JS/TS | `import X from 'lodash'` | `lodash` |
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| Python | `import django.core` | `django` |
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| Java | `import org.springframework.*` | `spring` or `spring-boot` |
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| Rust | `use tokio::runtime` | `tokio` |
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| Go | `import "github.com/gin-gonic/gin"` | `gin` |
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| Ruby | `require 'rails'` | `rails` |
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| PHP | `use Symfony\Component` | `symfony` |
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| C# | `using Microsoft.AspNetCore` | `AspNetCore` |
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**Query Strategy:**
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1. User-specified version → use as-is
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2. Detected from files → include in query
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3. No version found → use latest
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4. Always format: "{library} {version} {specific_feature}"
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## Best Practices
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**✅ Specific queries:**
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- "Django 5.0 class-based views authentication"
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- "Tokio 1.35 async runtime spawning tasks"
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- "Spring Boot 3.2 @RestController validation"
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**❌ Vague queries:**
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- "authentication"
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- "async programming"
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**Skip resolve if ID known:**
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```
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query-docs("/django/django", "Django 5.0 ORM filtering") # Direct
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```
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**Common ID patterns:**
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- GitHub: `/{owner}/{repo}` (e.g., `/vercel/next.js`)
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- Docs: `/{domain}` (e.g., `/tailwindcss.com/docs`)
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## Error Handling
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| Error | Action |
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|-------|--------|
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| 404 Not Found | Try alternative names, ask user |
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| 429 Rate Limited | Wait 60s, retry (set CONTEXT7_API_KEY for higher limits) |
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| Multiple matches | Present top 3, ask clarification |
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| Empty results | Broader query or fallback to web search |
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## Example (Multi-Language)
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```python
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# Python: Django REST API
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Task: "Add REST views with Django"
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1. grep_search("django", "requirements.txt") → "django==5.0.2"
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2. resolve-library-id("django", "REST API views") → /django/django
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3. query-docs("/django/django", "Django 5.0 class-based views REST") → docs
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4. Implement with verified APIs
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```
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```rust
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// Rust: Tokio Async
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Task: "Async HTTP with Tokio"
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1. grep_search("tokio", "Cargo.toml") → 'tokio = "1.35"'
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2. query-docs("/tokio-rs/tokio", "tokio 1.35 async HTTP runtime") → docs
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3. Use: Runtime::new() ✅ NOT: Runtime::init() ❌
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```
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```java
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// Java: Spring Boot
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Reviewer detecting Spring Boot 3.2 from pom.xml
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1. query-docs("/spring-projects/spring-boot", "Spring Boot 3.2 @RequestMapping")
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2. Flag: Use @GetMapping instead of @RequestMapping in v3.2
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```
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## MCP Tools
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**resolve-library-id** → Search library by name, returns ID
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**query-docs** → Fetch docs by ID, returns snippets
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---
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Use liberally to prevent hallucinated APIs. Cache results in FINDINGS.md.
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