Building MCP Servers

from fastmcp import FastMCP

mcp = FastMCP("my-tools")


@mcp.tool()
def ping_host(host: str) -> str:
    """Ping a host and return whether it is reachable.

    Args:
        host: The hostname or IP address to ping.
    """
    import subprocess

    result = subprocess.run(
        ["ping", "-c", "3", host],
        capture_output=True,
        text=True,
        timeout=10,
    )
    if result.returncode == 0:
        return f"Host {host} is reachable.\n{result.stdout}"
    return f"Host {host} is unreachable.\n{result.stderr}"


@mcp.tool()
def get_system_uptime() -> str:
    """Return the system uptime of the server running this MCP instance."""
    import subprocess

    result = subprocess.run(["uptime"], capture_output=True, text=True)
    return result.stdout.strip()

fastmcp run server.py --transport streamable-http --host 0.0.0.0 --port 8000

my-mcp-server/
  server.py           # Tool definitions
  pyproject.toml       # Dependencies and metadata
  Dockerfile           # Container build
  .env.example         # Environment variable template

[project]
name = "my-mcp-server"
version = "0.1.0"
requires-python = ">=3.12"
dependencies = [
    "fastmcp>=2.0",
]

[project.scripts]
serve = "server:main"

FROM python:3.12-slim

WORKDIR /app
COPY pyproject.toml .
COPY server.py .

RUN pip install --no-cache-dir .

EXPOSE 8000

CMD ["fastmcp", "run", "server.py", "--transport", "streamable-http", "--host", "0.0.0.0", "--port", "8000"]

docker build -t my-mcp-server .
docker run -p 8000:8000 my-mcp-server

import httpx
from fastmcp import FastMCP

mcp = FastMCP("async-tools")


@mcp.tool()
async def query_api(endpoint: str) -> str:
    """Query an external REST API and return the JSON response.

    Args:
        endpoint: The full URL to query.
    """
    async with httpx.AsyncClient() as client:
        response = await client.get(endpoint, timeout=30)
        response.raise_for_status()
        return response.text