MCP

An MCP server that adds two numbers has no opinion about who is calling it. One that posts to a social account has to answer a question before it can do anything at all: whose account? There are two workable answers. You can build a multi-tenant server that authenticates every caller and looks up the account they own, which is the shape Add GitHub OAuth to a FastMCP Server builds. Or you can build one process that acts as exactly one account, reads that account out of its own environment, and runs on the same machine as the client calling it. ...

Add Per-Plan Rate Limiting to a FastMCP Server on macOS closes its troubleshooting with “back it with Redis (shared, atomic counters) if you run several instances behind a load balancer”, and Add Observability to a FastMCP Server on macOS adds a /health endpoint “for load balancers”. Neither article puts a load balancer in front of anything. This one does, and the first thing that happens is that the server stops working. ...

Generate Synthetic JSON Requests to Test an API on macOS built two generators and a CLI that fires batches at an order-intake API. This article puts the same generators behind an MCP server, so an agent can preview a payload, check the target, and trigger a batch by asking for one. Wrapping a generator in tools is the easy half. The half worth attention is the control surface: which decisions the caller gets to make and which ones the server keeps. A model that can pick the destination of a traffic generator is a server-side request forgery primitive with a friendly name, and a model that can pick the batch size can turn one sentence into fifty thousand POSTs. Here the target comes from the environment and the batch size is capped, so the tools stay useful without handing over either decision. ...

Most teams have a procedure that only lives in someone’s head. Cutting release notes, triaging a breaking change, prepping an on-call handoff: five steps, done slightly differently every time, and badly the week the person who knows them is on vacation. MCP gives you three primitives to fix that, and the interesting one is the least used. Tools are called by the model. Resources are read for context. Prompts are chosen by a person: named, parameterized templates a client surfaces as a slash command. That makes a prompt the natural home for a procedure — the user picks it, fills in one argument, and the model runs the same five steps in the same order every time. ...

A resource that returns a picture is the most demanding shape an MCP resource takes. It has to survive base64 encoding, arrive with a MIME type the client will accept, stay small enough to attach, and — if the picture is meant to reflect something live — return different bytes the next time the same URI is read. Serve Resources Well from an MCP Server on macOS covered the shapes of resources with an eight-byte PNG magic number standing in for a binary body. This article replaces that stub with a real image: a bar chart rendered on every read from state that anything can change, packaged so uvx runs it from a local directory, and wired into opencode so a model can read it, watch it change, and read it again. ...

opencode attaches an MCP server in a single command, with no config file to hand-edit and no JSON to get wrong. Everything after the -- separator is the command that launches the server, and because uvx resolves the package on first launch, there is nothing to install beforehand either: opencode mcp add hello -- uvx mcp-hello-server This tutorial uses that command to attach mcp-hello-server — a small FastMCP server on PyPI exposing two tools, server_info and greet — then drives it from a free model. You will confirm the server connects, prove the launch command works without involving a model at all, pin the same server to a single project instead of your whole machine, and finally ask North Mini Code Free to say hello to Alice in Japanese. ...

The read-only Postgres MCP server built its safety on the database server: a SELECT-only role, a read-only transaction, a statement timeout, all enforced by a process on the other side of a socket. SQLite has none of that machinery. There is no server, no accounts, no GRANT. The database is a file, the engine runs inside your process, and any connection that can open the file read-write can do anything to it. ...

Give a language model a database tool and the obvious failure mode is not a clever exploit. It is a well-meaning model running DELETE FROM orders because a prompt told it to “clean up test data,” or issuing SELECT * FROM events against a billion-row table and stalling everything behind it. A database MCP server has to assume the caller is careless, and sometimes hostile. In this tutorial you will build a FastMCP server that exposes a Postgres database to an MCP client as strictly read-only, with the safety built in layers so no single mistake opens a hole: ...

Packaging an MCP server as a Docker image gives clients one launch command with no Python, no uv, and no virtual environment to manage on the host: they run the container. This tutorial builds a small, non-root image for a FastMCP server with a multi-stage build, runs it over stdio the way a client does, and wires it into a client’s .mcp.json with docker run. The build uses uv in the builder stage and copies only the finished virtual environment into a slim runtime stage, so the final image carries the app and its dependencies — not the build toolchain. ...

An installable MCP server needs the same release discipline as any Python package: lint and test every change, build the artifact, and publish on a tagged release. This tutorial wires that pipeline with GitHub Actions and uv — ruff for linting and formatting, pytest for tests, uv build for the wheel/sdist, and PyPI trusted publishing (OIDC, no stored token) on a version tag. It is the CI/CD companion to Publish a FastMCP Server to PyPI and Run It Anywhere with uvx. ...