mcp-patterns
Model Context Protocol (MCP) server patterns for building integrations with Claude Code. Triggers on: mcp server, model context protocol, tool handler, mcp resource, mcp tool.
What this skill does
# MCP Patterns
Model Context Protocol (MCP) server patterns for building integrations with Claude Code.
## Basic MCP Server (Python)
```python
from mcp.server import Server
from mcp.server.stdio import stdio_server
app = Server("my-server")
@app.list_tools()
async def list_tools():
return [
{
"name": "my_tool",
"description": "Does something useful",
"inputSchema": {
"type": "object",
"properties": {
"query": {"type": "string", "description": "Search query"}
},
"required": ["query"]
}
}
]
@app.call_tool()
async def call_tool(name: str, arguments: dict):
if name == "my_tool":
result = await do_something(arguments["query"])
return {"content": [{"type": "text", "text": result}]}
raise ValueError(f"Unknown tool: {name}")
async def main():
async with stdio_server() as (read_stream, write_stream):
await app.run(read_stream, write_stream, app.create_initialization_options())
if __name__ == "__main__":
import asyncio
asyncio.run(main())
```
## Project Layout
```
my-mcp-server/
├── src/
│ └── my_server/
│ ├── __init__.py
│ ├── server.py # Main server logic
│ ├── tools.py # Tool handlers
│ └── resources.py # Resource handlers
├── pyproject.toml
└── README.md
```
## Claude Desktop Configuration
### Basic Configuration
```json
{
"mcpServers": {
"my-server": {
"command": "python",
"args": ["-m", "my_server"],
"env": {
"MY_API_KEY": "your-key-here"
}
}
}
}
```
### With uv (Recommended)
```json
{
"mcpServers": {
"my-server": {
"command": "uv",
"args": ["run", "--directory", "/path/to/my-server", "python", "-m", "my_server"],
"env": {
"MY_API_KEY": "your-key-here"
}
}
}
}
```
## Quick Reference
| Pattern | Use Case | Reference |
|---------|----------|-----------|
| Tool validation | Input sanitization with Pydantic | `./references/tool-patterns.md` |
| Error handling | Graceful failure responses | `./references/tool-patterns.md` |
| Multiple tools | CRUD-style tool registration | `./references/tool-patterns.md` |
| Static resources | Config/settings exposure | `./references/resource-patterns.md` |
| Dynamic resources | Database-backed resources | `./references/resource-patterns.md` |
| Environment auth | API key from env vars | `./references/auth-patterns.md` |
| OAuth tokens | Token refresh with TTL | `./references/auth-patterns.md` |
| SQLite cache | Persistent state storage | `./references/state-patterns.md` |
| In-memory cache | TTL-based caching | `./references/state-patterns.md` |
| Manual testing | Quick validation script | `./references/testing-patterns.md` |
| pytest async | Unit tests for tools | `./references/testing-patterns.md` |
## Common Issues
| Issue | Solution |
|-------|----------|
| Server not starting | Check `command` path, ensure dependencies installed |
| Tool not appearing | Verify `list_tools()` returns valid schema |
| Auth failures | Check env vars are set in config, not shell |
| Timeout errors | Add timeout to httpx calls, use async properly |
| JSON parse errors | Ensure `call_tool` returns proper content structure |
## Official Documentation
- https://modelcontextprotocol.io - MCP specification
- https://modelcontextprotocol.io/docs/concepts/tools - Tools reference
- https://modelcontextprotocol.io/docs/concepts/resources - Resources reference
- https://github.com/modelcontextprotocol/python-sdk - Python SDK
- https://github.com/modelcontextprotocol/servers - Official MCP servers
## Additional Resources
For detailed patterns, load:
- `./references/tool-patterns.md` - Validation, error handling, multi-tool registration
- `./references/resource-patterns.md` - Static and dynamic resource exposure
- `./references/auth-patterns.md` - Environment variables, OAuth token refresh
- `./references/state-patterns.md` - SQLite persistence, in-memory caching
- `./references/testing-patterns.md` - Manual test scripts, pytest async patterns
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