Model Context Protocol (MCP) for Elixir — server and client.

Noizu.MCP implements the Model Context Protocol so Elixir applications can expose MCP servers (over stdio or Streamable HTTP) and consume MCP servers as a client.

Defining a server

defmodule MyApp.MCP do
  use Noizu.MCP.Server,
    name: "myapp",
    version: "1.0.0",
    instructions: "Tools for MyApp."

  tool MyApp.MCP.GetWeather
end

defmodule MyApp.MCP.GetWeather do
  use Noizu.MCP.Server.Tool,
    description: "Get current weather for a location",
    annotations: [read_only_hint: true]

  input do
    field :location, :string, required: true, description: "City name or zip code"
    field :units, :enum, values: [:celsius, :fahrenheit], default: :celsius
  end

  @impl true
  def call(%{location: location, units: units}, _ctx) do
    {:ok, "Weather in #{location}: 21 degrees #{units}"}
  end
end

Run it over stdio (e.g. for Claude Code / Claude Desktop):

children = [{MyApp.MCP, transport: :stdio}]

See Noizu.MCP.Server for the full server API and Noizu.MCP.Server.Tool for the tool definition DSL.