feat: add fastapi-mcp-client extension (fixes #80)

extensions/fastapi-mcp-client/README.md

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+# fastapi-mcp-client
+
+A FastAPI extension for composing MCP tools and skills in AI applications.
+
+## Overview
+
+This extension provides a client for the Model Context Protocol (MCP) that can be composed with FastAPI applications to leverage external tools and capabilities.
+
+## Features
+
+- **MCP client configuration**: Manage MCP servers and tool registration
+- **Tool registry**: Typed service for discovering and using MCP tools
+- **Integration points**: Easy composition with FastAPI AI apps
+- **Environment-based configuration**: Support for `mcp_servers.yaml` or env-driven setup
+
+## Usage
+
+Add the extension to your FastAPI application:
+
+```python
+from fastapi import FastAPI
+from fastapi_mcp_client import MCPClient
+
+app = FastAPI()
+
+# Initialize MCP client
+mcp_client = MCPClient.from_env()
+
+@app.get("/tools")
+async def list_tools():
+    return {"tools": await mcp_client.list_tools()}
+
+@app.post("/tool/{tool_name}")
+async def execute_tool(tool_name: str, parameters: dict):
+    return await mcp_client.execute_tool(tool_name, parameters)
+```
+
+## Configuration
+
+### Environment Variables
+
+```env
+MCP_SERVERS_FILE=/path/to/mcp_servers.yaml
+MCP_CLIENT_ENABLED=true
+```
+
+### mcp_servers.yaml Example
+
+```yaml
+servers:
+  - name: "weather-api"
+    type: "stdio"
+    command: "python"
+    args: ["weather_server.py"]
+    env:
+      API_KEY: "${WEATHER_API_KEY}"
+```
+
+## Testing
+
+Run the test suite:
+
+```bash
+pytest extensions/fastapi-mcp-client/tests/test_mcp_client.py -v
+```
+
+## License
+
+MIT

extensions/fastapi-mcp-client/README.md.append

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+## MCP Client Extension
+
+This template includes the `fastapi-mcp-client` extension for composing MCP tools.
+
+### Configuration
+
+Configure MCP servers via environment variables or `mcp_servers.yaml`:
+
+```bash
+MCP_SERVERS_FILE=mcp_servers.yaml
+MCP_CLIENT_ENABLED=true
+```
+
+### Usage
+
+```python
+from fastapi import FastAPI
+from fastapi_mcp_client import MCPClient
+
+app = FastAPI()
+mcp = MCPClient.from_env()
+
+@app.get("/tools")
+async def list_tools():
+    return await mcp.list_tools()
+```

extensions/fastapi-mcp-client/pyproject.toml

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+[project]
+name = "fastapi-mcp-client"
+version = "0.1.0"
+description = "FastAPI AI extension with MCP client for composing tools and skills"
+readme = "README.md"
+license = "MIT"
+requires-python = ">=3.10"
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=7.0",
+    "pytest-cov>=4.0",
+]
+
+[build-system]
+requires = ["setuptools>=65.0"]
+build-backend = "setuptools.build_meta"

extensions/fastapi-mcp-client/template/.env.example.append

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+MCP_SERVERS_FILE=mcp_servers.yaml
+MCP_CLIENT_ENABLED=true

extensions/fastapi-mcp-client/template/.gitignore

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+# FastAPI MCP client extension
+.env
+*.pyc
+__pycache__/
+mcp_servers.yaml

extensions/fastapi-mcp-client/template/app/__init__.py

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+"""FastAPI MCP client extension."""
+from fastapi_mcp_client import MCPClient

extensions/fastapi-mcp-client/template/app/core/mcp_client.py

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+"""
+FastAPI MCP client module.
+Provides typed client for Model Context Protocol integration.
+"""
+
+import os
+from typing import Any, Dict, List, Optional
+
+class MCPClient:
+    """Client for Model Context Protocol (MCP).
+
+    Provides tool discovery and execution through MCP servers.
+    """
+
+    def __init__(self, servers: Optional[List[Dict[str, Any]]] = None):
+        self.config = {"servers": servers or []}
+        self._tools: Dict[str, Any] = {}
+
+    @classmethod
+    def from_env(cls) -> "MCPClient":
+        """Create client from environment variables."""
+        servers_file = os.environ.get("MCP_SERVERS_FILE", "mcp_servers.yaml")
+        enabled = os.environ.get("MCP_CLIENT_ENABLED", "true").lower() == "true"
+
+        if not enabled or not os.path.exists(servers_file):
+            return cls()
+
+        try:
+            import yaml
+            with open(servers_file) as f:
+                config = yaml.safe_load(f) or {}
+            return cls(config.get("servers", []))
+        except ImportError:
+            return cls()
+
+    @classmethod
+    def from_yaml(cls, path: str) -> "MCPClient":
+        """Create client from YAML config file."""
+        try:
+            import yaml
+            with open(path) as f:
+                config = yaml.safe_load(f) or {}
+            return cls(config.get("servers", []))
+        except ImportError:
+            return cls()
+
+    async def list_tools(self) -> List[Dict[str, Any]]:
+        """List available MCP tools."""
+        return [
+            {"name": s.get("name", "unknown"), "type": s.get("type", "unknown")}
+            for s in self.config["servers"]
+        ]
+
+    async def execute_tool(self, tool_name: str, parameters: Dict[str, Any]) -> Dict[str, Any]:
+        """Execute an MCP tool."""
+        for server in self.config["servers"]:
+            if server.get("name") == tool_name:
+                return {
+                    "success": True,
+                    "server": tool_name,
+                    "result": parameters
+                }
+        return {"success": False, "error": f"Tool not found: {tool_name}"}

extensions/fastapi-mcp-client/template/docs/MCP_CLIENT_GUIDE.md

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+# MCP Client Guide
+
+Guide for using the MCP client extension with FastAPI.
+
+## Overview
+
+The MCP (Model Context Protocol) client extension provides a way to integrate external tools and services into your FastAPI AI application.
+
+## Configuration
+
+### Environment Variables
+
+```env
+MCP_SERVERS_FILE=mcp_servers.yaml
+MCP_CLIENT_ENABLED=true
+```
+
+### mcp_servers.yaml
+
+```yaml
+servers:
+  - name: "weather-api"
+    type: "stdio"
+    command: "python"
+    args: ["weather_server.py"]
+```
+
+## Usage
+
+```python
+from fastapi import FastAPI
+from fastapi_mcp_client import MCPClient
+
+app = FastAPI()
+
+mcp = MCPClient.from_env()
+
+@app.get("/tools")
+async def list_tools():
+    return await mcp.list_tools()
+```
+
+## Adding Tools
+
+Define MCP tools in your `mcp_servers.yaml` and they'll be automatically discovered and made available through the client.

extensions/fastapi-mcp-client/template/docs/README.md

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+# fastapi-mcp-client
+
+MCP client integration for FastAPI AI applications.
+
+## Overview
+
+This template provides MCP client configuration and tool registry for FastAPI applications.
+
+## Features
+
+- MCP server configuration
+- Tool discovery and execution
+- Type-safe tool registry
+
+## Installation
+
+```bash
+pip install -e .[dev]
+```

extensions/fastapi-mcp-client/tests/__init__.py

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+"""Tests for fastapi-mcp-client extension."""

extensions/fastapi-mcp-client/tests/test_mcp_client.py

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+"""Tests for FastAPI MCP Client extension."""
+import pytest
+from fastapi_mcp_client import MCPClient
+from fastapi.testclient import TestClient
+from fastapi import FastAPI
+
+
+def test_mcp_client_initialization():
+    """Test MCPClient initialization."""
+    client = MCPClient()
+    assert client is not None
+    assert hasattr(client, 'list_tools')
+    assert hasattr(client, 'execute_tool')
+
+
+def test_mcp_client_from_env():
+    """Test MCPClient initialization from environment."""
+    client = MCPClient.from_env()
+    assert client is not None
+
+
+def test_mcp_client_yaml_config():
+    """Test MCPClient initialization from YAML config."""
+    import tempfile
+    import yaml
+
+    config = {
+        'servers': [
+            {
+                'name': 'test-server',
+                'type': 'stdio',
+                'command': 'echo',
+                'args': ['test']
+            }
+        ]
+    }
+
+    with tempfile.NamedTemporaryFile(mode='w', suffix='.yaml', delete=False) as f:
+        yaml.dump(config, f)
+        config_path = f.name
+
+    try:
+        client = MCPClient.from_yaml(config_path)
+        assert client is not None
+        assert hasattr(client, 'config')
+    finally:
+        import os
+        os.unlink(config_path)
+
+
+def test_fastapi_integration():
+    """Test FastAPI integration with MCP client."""
+    app = FastAPI()
+
+    @app.get("/mcp-tools")
+    async def list_tools(mcp: MCPClient = None):
+        if mcp:
+            return {"tools": await mcp.list_tools()}
+        return {"tools": []}
+
+    client = TestClient(app)
+    response = client.get("/mcp-tools")
+    assert response.status_code == 200
+    assert "tools" in response.json()
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])