MCP Client example: Chatbot CLI

client.py

import asyncio
from typing import Optional
from contextlib import AsyncExitStack

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

from anthropic import Anthropic
from dotenv import load_dotenv

load_dotenv()  # load environment variables from .env

class MCPClient:
    def __init__(self):
        # Initialize session and client objects
        self.session: Optional[ClientSession] = None
        self.exit_stack = AsyncExitStack()
        self.anthropic = Anthropic()

    async def connect_to_server(self, server_script_path: str):
        """Connect to an MCP server
        
        Args:
            server_script_path: Path to the server script (.py or .js)
        """
        is_python = server_script_path.endswith('.py')
        is_js = server_script_path.endswith('.js')
        if not (is_python or is_js):
            raise ValueError("Server script must be a .py or .js file")
            
        command = "python" if is_python else "node"
        server_params = StdioServerParameters(
            command=command,
            args=[server_script_path],
            env=None
        )
        
        stdio_transport = await self.exit_stack.enter_async_context(stdio_client(server_params))
        self.stdio, self.write = stdio_transport
        self.session = await self.exit_stack.enter_async_context(ClientSession(self.stdio, self.write))
        
        await self.session.initialize()
        
        # List available tools
        response = await self.session.list_tools()
        tools = response.tools
        print("\nConnected to server with tools:", [tool.name for tool in tools])

    async def process_query(self, query: str) -> str:
        """Process a query using Claude and available tools"""
        messages = [
            {
                "role": "user",
                "content": query
            }
        ]

        response = await self.session.list_tools()
        available_tools = [{ 
            "name": tool.name,
            "description": tool.description,
            "input_schema": tool.inputSchema
        } for tool in response.tools]

        # Initial Claude API call
        response = self.anthropic.messages.create(
            model="claude-3-5-sonnet-20241022",
            max_tokens=1000,
            messages=messages,
            tools=available_tools
        )

        # Process response and handle tool calls
        tool_results = []
        final_text = []

        for content in response.content:
            if content.type == 'text':
                final_text.append(content.text)
            elif content.type == 'tool_use':
                tool_name = content.name
                tool_args = content.input
                
                # Execute tool call
                result = await self.session.call_tool(tool_name, tool_args)
                tool_results.append({"call": tool_name, "result": result})
                final_text.append(f"[Calling tool {tool_name} with args {tool_args}]")

                # Continue conversation with tool results
                if hasattr(content, 'text') and content.text:
                    messages.append({
                      "role": "assistant",
                      "content": content.text
                    })
                messages.append({
                    "role": "user", 
                    "content": result.content
                })

                # Get next response from Claude
                response = self.anthropic.messages.create(
                    model="claude-3-5-sonnet-20241022",
                    max_tokens=1000,
                    messages=messages,
                )

                final_text.append(response.content[0].text)

        return "\n".join(final_text)

    async def chat_loop(self):
        """Run an interactive chat loop"""
        print("\nMCP Client Started!")
        print("Type your queries or 'quit' to exit.")
        
        while True:
            try:
                query = input("\nQuery: ").strip()
                
                if query.lower() == 'quit':
                    break
                    
                response = await self.process_query(query)
                print("\n" + response)
                    
            except Exception as e:
                print(f"\nError: {str(e)}")
    
    async def cleanup(self):
        """Clean up resources"""
        await self.exit_stack.aclose()

async def main():
    if len(sys.argv) < 2:
        print("Usage: python client.py <path_to_server_script>")
        sys.exit(1)
        
    client = MCPClient()
    try:
        await client.connect_to_server(sys.argv[1])
        await client.chat_loop()
    finally:
        await client.cleanup()

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

Hi there, can anyone help me with

import asyncio
from typing import Optional
from contextlib import AsyncExitStack
import logging
import json

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

from anthropic import Anthropic
from dotenv import load_dotenv

load_dotenv()  # load environment variables from .env
print("Environment variables loaded from .env file")

class MCPClient:
    def __init__(self):
        # Initialize session and client objects
        print("Initializing MCPClient...")
        self.session: Optional[ClientSession] = None
        self.exit_stack = AsyncExitStack()
        self.anthropic = Anthropic()
        print("MCPClient initialized successfully")

    async def connect_to_server(self, server_script_path: str):
        """Connect to an MCP server
        
        Args:
            server_script_path: Path to the server script (.py or .js)
        """
        print(f"Connecting to server with script: {server_script_path}")
        is_python = server_script_path.endswith('.py')
        is_js = server_script_path.endswith('.js')
        if not (is_python or is_js):
            print(f"Error: Invalid script type for {server_script_path}")
            raise ValueError("Server script must be a .py or .js file")
            
        command = "python" if is_python else "node"
        print(f"Using {command} to execute server script")
        server_params = StdioServerParameters(
            command=command,
            args=[server_script_path],
            env=None
        )
        
        print("Establishing stdio transport connection...")
        stdio_transport = await self.exit_stack.enter_async_context(stdio_client(server_params))
        self.stdio, self.write = stdio_transport
        print("Creating client session...")
        self.session = await self.exit_stack.enter_async_context(ClientSession(self.stdio, self.write))
        
        print("Initializing session...")
        await self.session.initialize()
        
        # List available tools
        print("Retrieving available tools...")
        response = await self.session.list_tools()
        tools = response.tools
        print("\nConnected to server with tools:", [tool.name for tool in tools])
        print(f"Total tools available: {len(tools)}")```
        
        
        I have this code but it is getting strucked at Initialing session forever. It is not showing any error or anything

Does your server.py file throw any error when you run "uv run server.py" command?

Hi, I have the same problem, my code runs until :
await self.session.initialize()
but then nothing happens. I don't get any errors in my server or client when I run these codes.

I'm hitting the following error:
Error: Error code: 400 - {'type': 'error', 'error': {'type': 'invalid_request_error', 'message': 'Your credit balance is too low to access the Anthropic API. Please go to Plans & Billing to upgrade or purchase credits.'}}
I don't think that I overused the API Key. Is it possible that the key is not consumed?

please how do I connect my server to the client. I'm kinda confuse cos both are on different folders

@anonscodex

It is mentioned in the documentation:

server_params = StdioServerParameters( command=command, args=[server_script_path], env=None )

Just add your mcp server's ".py / .js" file path in "args".

please how do I connect my server to the client. I'm kinda confuse cos both are on different folders

Simple. Just run in terminal "uv run client.py [\file path]"