PoC-AI-MCP/client/mcp_client.py

#!/usr/bin/env python3
"""
MCP Client - Integrates vLLM with MCP weather server
"""

import asyncio
import json
import os
from typing import Optional
from contextlib import asynccontextmanager

from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client
from openai import OpenAI


class MCPWeatherClient:
    """Client that connects vLLM to MCP weather server"""

    def __init__(self, vllm_url: str = "http://127.0.0.1:8000/v1", model: str = "qwen"):
        self.vllm_url = vllm_url
        self.model = model
        self.openai_client = OpenAI(
            api_key="EMPTY",  # vLLM doesn't need API key
            base_url=vllm_url
        )
        self.mcp_session: Optional[ClientSession] = None
        self.available_tools = []

    @asynccontextmanager
    async def connect_to_mcp(self, server_script_path: str):
        """Connect to MCP server via stdio"""
        server_params = StdioServerParameters(
            command="python",
            args=[server_script_path],
            env=None
        )

        async with stdio_client(server_params) as (read, write):
            async with ClientSession(read, write) as session:
                await session.initialize()
                self.mcp_session = session

                # List available tools
                tools_list = await session.list_tools()
                print(f"\nConnected to MCP server. Available tools:")
                for tool in tools_list.tools:
                    print(f"  - {tool.name}: {tool.description}")
                    self.available_tools.append(tool)

                yield session

    def mcp_tools_to_openai_format(self):
        """Convert MCP tools to OpenAI function calling format"""
        openai_tools = []

        for tool in self.available_tools:
            # Convert MCP tool schema to OpenAI format
            tool_def = {
                "type": "function",
                "function": {
                    "name": tool.name,
                    "description": tool.description or "",
                    "parameters": tool.inputSchema if tool.inputSchema else {
                        "type": "object",
                        "properties": {},
                        "required": []
                    }
                }
            }
            openai_tools.append(tool_def)

        return openai_tools

    async def call_mcp_tool(self, tool_name: str, arguments: dict):
        """Call an MCP tool and return the result"""
        if not self.mcp_session:
            raise RuntimeError("MCP session not initialized")

        result = await self.mcp_session.call_tool(tool_name, arguments)
        return result

    async def chat(self, user_message: str, max_iterations: int = 5):
        """
        Run a chat interaction with the model, handling tool calls via MCP

        Args:
            user_message: The user's question/message
            max_iterations: Maximum number of turns to prevent infinite loops
        """
        messages = [
            {
                "role": "system",
                "content": "You are a helpful assistant that can get weather information for cities. When asked about weather, use the get_weather tool."
            },
            {
                "role": "user",
                "content": user_message
            }
        ]

        tools = self.mcp_tools_to_openai_format()
        print(f"\nUser: {user_message}\n")

        for iteration in range(max_iterations):
            # Call the model
            response = self.openai_client.chat.completions.create(
                model=self.model,
                messages=messages,
                tools=tools if tools else None,
                tool_choice="auto" if tools else None
            )

            assistant_message = response.choices[0].message

            # Add assistant response to messages
            messages.append({
                "role": "assistant",
                "content": assistant_message.content,
                "tool_calls": [
                    {
                        "id": tc.id,
                        "type": tc.type,
                        "function": {
                            "name": tc.function.name,
                            "arguments": tc.function.arguments
                        }
                    }
                    for tc in (assistant_message.tool_calls or [])
                ]
            })

            # Check if model wants to call tools
            if assistant_message.tool_calls:
                print(f"Assistant wants to call {len(assistant_message.tool_calls)} tool(s):\n")

                # Process each tool call
                for tool_call in assistant_message.tool_calls:
                    function_name = tool_call.function.name
                    function_args = json.loads(tool_call.function.arguments)

                    print(f"  Calling tool: {function_name}")
                    print(f"  Arguments: {function_args}")

                    # Call the MCP tool
                    mcp_result = await self.call_mcp_tool(function_name, function_args)

                    # Extract content from MCP result
                    if mcp_result.content:
                        # Handle different content types
                        result_text = ""
                        for content in mcp_result.content:
                            if hasattr(content, 'text'):
                                result_text += content.text
                            else:
                                result_text += str(content)

                        print(f"  Result: {result_text}\n")

                        # Add tool result to messages
                        messages.append({
                            "role": "tool",
                            "tool_call_id": tool_call.id,
                            "content": result_text
                        })
                    else:
                        print(f"  Result: No content returned\n")
                        messages.append({
                            "role": "tool",
                            "tool_call_id": tool_call.id,
                            "content": "No result"
                        })

                # Continue the loop to get final response
                continue

            # No tool calls, this is the final response
            if assistant_message.content:
                print(f"Assistant: {assistant_message.content}\n")
                return assistant_message.content
            else:
                print("Assistant: (no response)")
                return None

        print("\nReached maximum iterations")
        return None


async def main():
    """Main function to run the client"""
    import sys

    # Get the MCP server script path
    script_dir = os.path.dirname(os.path.abspath(__file__))
    project_root = os.path.dirname(script_dir)
    mcp_server_path = os.path.join(project_root, "mcp-server", "weather_server.py")

    if not os.path.exists(mcp_server_path):
        print(f"Error: MCP server script not found at {mcp_server_path}")
        sys.exit(1)

    # Create client
    client = MCPWeatherClient()

    # Connect to MCP server and run chat
    async with client.connect_to_mcp(mcp_server_path):
        # Example question about weather
        question = "What's the weather like in Paris?"

        if len(sys.argv) > 1:
            question = " ".join(sys.argv[1:])

        await client.chat(question)


if __name__ == "__main__":
    asyncio.run(main())