mcp-registry

A small, end-to-end walkthrough of the MLflow MCP Server Registry: build MCP servers with FastMCP, call them with a FastMCP client, then register them in MLflow so they are discoverable — with versions, access endpoints, and auto-discovered tools.

The repo has three moving parts:

Part	Path	What it does
MCP servers	src/	Two FastMCP servers — a toy greeting server and a real PostgreSQL explorer
MCP clients	clients/	Thin FastMCP clients that invoke tools over streamable HTTP
Registry utility	mlflow_mcp_registry_util.py	Registers servers with MLflow, refreshes their tools, lists access endpoints

---

Requirements

• Python ≥ 3.13
• An MLflow tracking server (v3.15+) running locally — the registry APIs are server-side
• PostgreSQL, if you want to exercise the PostgreSQL server
• uv (the repo ships a uv.lock)

Dependencies (pyproject.toml): fastmcp>=3.4.7, mlflow>=3.15.1, psycopg2 + psycopg2-binary, python-dotenv.

uv sync

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Configuration

The PostgreSQL server reads its connection settings from a .env file in the repo root (loaded via python-dotenv). .env is gitignored — create your own:

PGHOST=localhost
PGPORT=5432
PGUSER=root
PGPASSWORD=root
PGSSLMODE=prefer
PGADMINDB=postgres

Variable	Default	Purpose
PGHOST	localhost	Server host
PGPORT	5432	Server port
PGUSER	root	Login role
PGPASSWORD	root	Password
PGSSLMODE	prefer	libpq SSL mode
PGADMINDB	postgres	Database used for server-wide queries (ListDatabases)

src/simple_server.py needs no configuration.

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1. Start an MLflow tracking server

mlflow_mcp_registry_util.py points at http://127.0.0.1:5000. The repo already contains a mlflow.db (gitignored) from a SQLite-backed run:

uv run mlflow server --backend-store-uri sqlite:///mlflow.db --host 127.0.0.1 --port 5000

If your server lives elsewhere, edit the mlflow.set_tracking_uri(...) call at the top of mlflow_mcp_registry_util.py.

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2. Run an MCP server

Both servers bind port 8000 over streamable HTTP (http://localhost:8000/mcp), so run one at a time — or change the port in the mcp.run(...) call.

Simple greeting server — two tools, Greeting and Sendoff:

uv run python src/simple_server.py

PostgreSQL explorer — read-only introspection of a live PostgreSQL server:

uv run python src/postgresql_mcp.py

Or via the FastMCP CLI:

uv run fastmcp run src/postgresql_mcp.py --transport http --port 8000

PostgreSQL tools

Tool	Arguments	Returns
ListDatabases	—	Non-template databases with owner and pretty-printed size
ListSchemas	database	User-defined schemas (system schemas and temp schemas excluded)
ListTables	database, schema	Tables and views in the schema, with table_type
ListTableColumns	database, schema, table	Column name, type, nullability, default — in ordinal order
ListTableRelations	database, schema, table	Foreign keys split into outgoing (this table → others) and incoming (others → this table)
ListSchemaRelations	database, schema	Flat edge list from_table.from_column → to_table.to_column for the whole schema — an ERD in list form

Every tool goes through _query(), which opens a fresh connection to the named database, runs a single parameterised SELECT through a RealDictCursor, and closes the connection. Nothing writes.

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3. Call a server from a client

With a server running on port 8000:

uv run python clients/postgres_server_client.py   # calls ListDatabases, prints each database name
uv run python clients/simple_server_client.py     # calls the greeting tool with "Ford"

clients/postgres_server_client.py unwraps the FastMCP result: each item in result.content carries a JSON text payload, which it parses and reads database from.

Note: clients/simple_server_client.py calls client.call_tool("greet", ...), but the tool in src/simple_server.py is registered under the name Greeting (greet is only the Python function name). Use "Greeting" for the call to resolve.

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4. Register servers with MLflow

mlflow_mcp_registry_util.py holds four coroutines, each demonstrating one registry API:

register_postgresql_mcp_server()

Registers a remote server — one that is already running and reachable over HTTP:

mlflow.genai.register_mcp_server(
    server_json={
        "name": "io.github.pavanjava/postgresql-server",
        "version": "0.1.0",
        "description": "PostgreSQL FastMCP server exposing DB tools",
        "remotes": [{"url": "http://localhost:8000/mcp", "type": "streamable-http"}],
    },
    status="active",
    source="local dev server via fastmcp",
    create_access_endpoints_from_remotes=True,
)

create_access_endpoints_from_remotes=True turns each entry in remotes into an MLflow access endpoint, so consumers can resolve a connection URL from the registry instead of hardcoding it.

register_qdrant_mcp_server()

Registers a packaged server instead — no running process required. The entry describes how to launch it (uvx mcp-server-qdrant over stdio) and declares its environment variables, including which are required and which are secret (QDRANT_API_KEY).

discover_tools()

Calls refresh_mcp_server_version_tools(...). MLflow connects to the registered server version, enumerates its tools, and persists them on the version — after which server_version.tools lists the discovered tool names. This requires the server to actually be reachable.

list_endpoints()

Calls search_mcp_access_endpoints(server_name=...) and prints each endpoint's URL, transport type, and the server version it resolves to.

Running it

The __main__ block runs one coroutine at a time; the rest are commented out. Uncomment the one you want:

if __name__ == "__main__":
    # asyncio.run(register_postgresql_mcp_server())
    asyncio.run(register_qdrant_mcp_server())
    # asyncio.run(discover_tools())
    # asyncio.run(list_endpoints())

uv run python mlflow_mcp_registry_util.py

Registered servers then show up under the MCP Servers section of the MLflow UI at http://127.0.0.1:5000.

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Suggested end-to-end path

1. Start MLflow on port 5000.
2. Start the PostgreSQL MCP server on port 8000.
3. Verify it answers: uv run python clients/postgres_server_client.py.
4. Register it: uncomment register_postgresql_mcp_server() and run the util.
5. Discover its tools: switch to discover_tools() and run again — the six tools above should print.
6. Inspect its access endpoint: switch to list_endpoints().
7. Browse the result in the MLflow UI.

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Repository layout

.
├── src/
│   ├── simple_server.py        # FastMCP "My MCP Server" — Greeting + Sendoff tools
│   └── postgresql_mcp.py       # FastMCP "PostgreSQL Explorer" — 6 read-only introspection tools
├── clients/
│   ├── simple_server_client.py     # calls a tool on the greeting server
│   └── postgres_server_client.py   # calls ListDatabases and prints database names
├── mlflow_mcp_registry_util.py # MLflow MCP registry: register / refresh tools / list endpoints
├── pyproject.toml
└── uv.lock

mlflow.db, .env, .venv, and .idea are gitignored.