Fastmcp

fastmcp

Build MCP (Model Context Protocol) servers in Python with FastMCP

What This Skill Does

This skill provides production-tested patterns, templates, and error prevention for building MCP servers with FastMCP in Python. It covers:

• Server Creation: Tools, resources, resource templates, and prompts
• API Integration: OpenAPI/Swagger auto-generation, FastAPI conversion, manual integration
• Cloud Deployment: FastMCP Cloud requirements and common pitfalls
• Error Prevention: 15 documented errors with solutions
• Production Patterns: Self-contained architecture, connection pooling, caching, retry logic
• Context Features: Elicitation, progress tracking, sampling
• Testing: Unit and integration testing patterns
• Client Configuration: Claude Desktop, Claude Code CLI

When to Use This Skill

Use this skill when you need to:

• Build an MCP server to expose tools/resources/prompts to LLMs
• Integrate an external API with Claude (via MCP)
• Deploy an MCP server to FastMCP Cloud
• Convert an OpenAPI/Swagger spec to MCP
• Convert a FastAPI app to MCP
• Wrap a database, file system, or service for LLM access
• Debug MCP server errors (circular imports, module-level issues, async/await)
• Test MCP servers with FastMCP Client
• Implement elicitation (user input during execution)
• Add progress tracking to long-running operations
• Use sampling (LLM completions from within tools)

Don't use this skill if:

• You're building an MCP client (not server)
• You're using a different MCP framework (not FastMCP)
• You're working in a language other than Python
• You're building with Anthropic's TypeScript SDK for MCP

Auto-Trigger Keywords

This skill should automatically trigger when you mention:

Primary Keywords

• fastmcp, fast mcp, FastMCP
• MCP server, mcp server, MCP server python, python mcp server
• model context protocol, model context protocol python
• mcp tools, mcp resources, mcp prompts
• mcp integration, mcp framework

Use Case Keywords

• build mcp server, create mcp server, make mcp server
• python mcp, mcp python, mcp with python
• integrate api with claude, expose api to llm, api for claude
• openapi to mcp, swagger to mcp, fastapi to mcp
• mcp cloud, fastmcp cloud, deploy mcp
• mcp testing, test mcp server

Error Keywords

• mcp server not found, no server object found
• circular import fastmcp, import error mcp
• module-level server, fastmcp cloud deployment
• mcp async await, mcp context injection
• resource uri scheme, invalid resource uri
• pydantic validation mcp, mcp json serializable

Feature Keywords

• mcp elicitation, user input during tool execution
• mcp progress tracking, progress updates mcp
• mcp sampling, llm from mcp tool
• resource templates mcp, dynamic resources
• tool transformation mcp, client handlers

Integration Keywords

• openapi integration, swagger integration, fastapi mcp
• api wrapper mcp, database mcp, file system mcp
• connection pooling mcp, caching mcp, retry logic mcp

Claude Integration Keywords

• claude desktop mcp, claude code mcp
• claude_desktop_config.json, mcp configuration
• expose tools to claude, claude tools

Errors Prevented

This skill prevents 15 common errors:

1. Missing server object - Module-level export for FastMCP Cloud
2. Async/await confusion - Proper async/sync patterns
3. Context not injected - Type hints for context parameter
4. Resource URI syntax - Missing scheme prefixes
5. Resource template mismatch - Parameter name alignment
6. Pydantic validation errors - Type hint consistency
7. Transport/protocol mismatch - Client/server compatibility
8. Import errors - Editable package installation
9. Deprecation warnings - FastMCP v2 migration
10. Port conflicts - Address already in use
11. Schema generation failures - Unsupported type hints
12. JSON serialization - Non-serializable objects
13. Circular imports - Factory function anti-patterns
14. Python version compatibility - Deprecated methods
15. Import-time execution - Async resource creation

What's Included

Templates (12)

• basic-server.py - Minimal working server
• tools-examples.py - Sync/async tools
• resources-examples.py - Static/dynamic resources
• prompts-examples.py - Prompt templates
• openapi-integration.py - OpenAPI auto-generation
• api-client-pattern.py - Manual API integration
• client-example.py - Testing with Client
• error-handling.py - Structured errors with retry
• self-contained-server.py - Production pattern
• .env.example - Environment variables
• requirements.txt - Package dependencies
• pyproject.toml - Package configuration

Reference Docs (6)

• common-errors.md - 15 errors with solutions
• cloud-deployment.md - FastMCP Cloud guide
• cli-commands.md - FastMCP CLI reference
• integration-patterns.md - OpenAPI, FastAPI patterns
• production-patterns.md - Self-contained architecture
• context-features.md - Elicitation, progress, sampling

Scripts (3)

• check-versions.sh - Verify package versions
• test-server.sh - Test with FastMCP Client
• deploy-cloud.sh - Deployment checklist

Quick Start

Install the Skill

cd /path/to/claude-skills
./scripts/install-skill.sh fastmcp

Use the Skill

Just mention "fastmcp" or "build an mcp server" in your conversation with Claude Code, and the skill will automatically load.

Example prompts:

• "Help me build a FastMCP server"
• "Create an MCP server that wraps this API"
• "Convert this OpenAPI spec to an MCP server"
• "My MCP server has a circular import error"
• "Deploy my MCP server to FastMCP Cloud"

Production Validation

Tested With:

• FastMCP 2.12.0+
• Python 3.10, 3.11, 3.12
• FastMCP Cloud deployments
• OpenAPI integrations
• FastAPI conversions

Based On:

• Official FastMCP documentation
• Real-world production patterns
• SimPro MCP server case study
• FastMCP Cloud deployment experience

Package Info

• Package: fastmcp>=2.12.0
• Python: >=3.10
• Repository: https://github.com/jlowin/fastmcp
• Cloud: https://fastmcp.cloud
• Context7: /jlowin/fastmcp

Related Skills

• openai-api - OpenAI API integration
• claude-api - Claude API integration
• cloudflare-worker-base - Deploy as Cloudflare Worker
• google-gemini-api - Gemini API integration

Skill Metadata

• Version: 1.0.0
• License: MIT
• Token Savings: 85-90%
• Errors Prevented: 15
• Production Tested: ✅
• Last Updated: 2025-10-28

---

Questions or issues? Check the templates and references in this skill, or consult the official FastMCP documentation at https://github.com/jlowin/fastmcp