Build Your Own MCP Server in Python

uv init docs-server && cd docs-server
uv add "mcp[cli]"

from mcp.server.fastmcp import FastMCP

mcp = FastMCP("docs")

DOCS = {
    "deploy": "Deploys run from main via `make deploy`. Staging deploys on every merge.",
    "oncall": "On-call rotates Mondays. Page via #oncall-urgent.",
}

@mcp.tool()
def list_docs() -> list[str]:
    """List the IDs of all internal docs."""
    return sorted(DOCS)

@mcp.tool()
def read_doc(doc_id: str) -> str:
    """Read an internal doc by its ID."""
    if doc_id not in DOCS:
        raise ValueError(f"Unknown doc '{doc_id}'. Call list_docs first.")
    return DOCS[doc_id]

@mcp.tool()
def edit_doc(doc_id: str, new_content: str) -> str:
    """Replace the content of an existing doc."""
    if doc_id not in DOCS:
        raise ValueError(f"Unknown doc '{doc_id}'.")
    DOCS[doc_id] = new_content
    return f"Updated {doc_id}"

if __name__ == "__main__":
    mcp.run()  # stdio transport by default

@mcp.resource("docs://index")
def docs_index() -> str:
    """All doc IDs, one per line."""
    return "\n".join(sorted(DOCS))

@mcp.resource("docs://{doc_id}")
def doc_resource(doc_id: str) -> str:
    """A single doc as a resource."""
    return DOCS[doc_id]

@mcp.prompt()
def summarize_doc(doc_id: str) -> str:
    """Summarize a doc for a new teammate."""
    return f"Read the doc '{doc_id}' and summarize it in 5 bullets for someone in their first week."

uv run mcp dev server.py

claude mcp add --transport stdio docs -- uv run --directory /path/to/docs-server server.py