Model Context Protocol (MCP) is an open standard, created by Anthropic and now developed as a community open-source project, for connecting an LLM to external tools and data — instead of writing a bespoke integration for every editor or app you want a model to work inside, you write one MCP server and any MCP-compatible client (Claude Desktop, an IDE plugin, a custom app) can talk to it. Running it locally means the server process — and whatever local files, databases, or scripts it touches — never leaves your machine.
Step-by-Step Implementation
1. Initialize MCP Server: Create a project using Node.js or Python with the official SDK libraries.
2. Register Custom Tools: Declare tools, schemas, and resource resolvers inside the server's manifest.
3. Link to Client Editor: Add the server's execution path and environment keys to your desktop configuration file.
# Custom Model Context Protocol (MCP) tool server
from mcp.server.fastmcp import FastMCP
import sys
# Initialize FastMCP server instance
mcp = FastMCP("Local Workspace Assistant")
@mcp.tool()
def read_system_log(lines: int = 50) -> str:
"""Reads local system execution logs for debugging agent behaviors."""
try:
with open("workspace_logs.txt", "r") as f:
log_data = f.readlines()
return "".join(log_data[-lines:])
except Exception as e:
return f"Error reading logs: {str(e)}"
if __name__ == "__main__":
# Run server using Stdio transport for editor integration
mcp.run()
| Transport Layout | Latency Profile | Security Restriction |
|---|---|---|
| Stdio Transport | Sub-millisecond local process piping | Limited to same-machine execution |
| SSE Transport | Low latency, supports remote hosts | Requires HTTP server configuration and authentication |
Once the server is registered with your client's config file, the model can call read_system_log (or any tool you register) the same way it would call a built-in tool — the client handles spawning the server process and routing JSON-RPC messages back and forth over stdio.
Practical Challenge
Implement a new tool in the MCP server that lists files in the workspace and handles sub-directory recursion limits.
Concept Check
Sources & Further Reading
- Model Context Protocol — Specification — the official protocol spec (transports, JSON-RPC message shapes, tool schemas).
- modelcontextprotocol/modelcontextprotocol (GitHub) — the official open-source spec and reference docs, created by Anthropic and maintained as a community project.
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