Name: Emcee
Author: mattt

LABSCO SUMMARY

The tool list is whatever the spec says, so you shape it with jq before the server ever starts.

That is the trick worth knowing: piping the spec through jq to keep one path means the assistant sees one tool instead of dozens, without a config format to learn. It is the fastest route to an MCP server for a service that does not have one — especially a service you are building yourself and already have a spec for.

What it is

A command-line tool that reads an OpenAPI specification and serves it as an MCP server, so any documented web API becomes tools an assistant can call.

What you get

Tools generated from a spec's operations, with their input schemas, straight from a URL or a local file
Authentication handled for you: --bearer-auth, --basic-auth and --raw-auth, each becoming the right Authorization header
1Password secret references in place of literal credentials, using op://vault/item/field with the op CLI signed in
Rate and reliability controls — --rps to cap requests per second, --retries defaulting to 3, and --timeout defaulting to 1m0s
Spec transformation through ordinary Unix tools: filter operations with jq before handing the spec over, so only the tools you want exist
HTTP QUERY support per RFC 10008, including the x-query compatibility extension on older OpenAPI 3.x specs, registered as read-only and idempotent
Stdio transport over JSON-RPC 2.0

Requirements

The binary — brew install mattt/tap/emcee, the installer script, a Docker image, or built from source with go 1.24 or later. Then one line of client config: the emcee command plus the spec URL. Note that credentials are not used when downloading a spec from a URL, so a spec behind auth has to be fetched yourself and passed as a local file. Only tools are provided — no resources, prompts or sampling.

Setup effort

One command — brew install mattt/tap/emcee

See installation options

USE CASES

01

Using an API that has no MCP server

Hand emcee its OpenAPI spec and get tools without writing an integration.

02

Exposing only part of a large API

Filter the spec with jq so just the operations you want become tools.

03

Keeping a token out of your config file

Pass a 1Password secret reference instead of the literal credential.

04

Being a polite client of someone else's service

Cap requests per second and set a timeout so an eager agent does not hammer it.

BEFORE YOU INSTALL

What to know first

Requires

emcee on PATH

Where it runs

Both documented setups run the server on your machine.

INSTALLATION

Connect your client

Server setup

TERMINAL

brew install mattt/tap/emcee

MCP Clients

Claude Desktop

CLAUDE DESKTOP · JSON

{
  "mcpServers": {
    "weather": {
      "command": "emcee",
      "args": [
        "https://api.weather.gov/openapi.json"
      ]
    }
  }
}

Claude Desktop — 1Password

CLAUDE DESKTOP — 1PASSWORD · JSON

{
  "mcpServers": {
    "twitter": {
      "command": "emcee",
      "args": [
        "--bearer-auth=op://shared/x/credential",
        "https://api.twitter.com/2/openapi.json"
      ]
    }
  }
}

Emcee