Macro for generating MCP tool modules from a concise DSL.

Each tool block becomes a nested module that uses Anubis.Server.Component with schema definitions, execute wrappers, and metadata.

Usage

defmodule MyApp.Tools do
  use ClaudeCode.MCP.Server, name: "my-tools"

  tool :add do
    description "Add two numbers"

    field :x, :integer, required: true
    field :y, :integer, required: true

    def execute(%{x: x, y: y}) do
      {:ok, "#{x + y}"}
    end
  end

  tool :get_time do
    description "Get current UTC time"

    def execute(_params) do
      {:ok, DateTime.utc_now() |> to_string()}
    end
  end
end

Generated Module Structure

Each tool block generates a nested module (e.g., MyApp.Tools.Add) that:

• Uses Anubis.Server.Component with type: :tool
• Has a schema block for Peri-validated input parameters
• Has input_schema/0 returning JSON Schema (via Anubis Component)
• Has execute/2 accepting (params, frame) and delegating to the user's execute function

Execute Function

The user's execute function can be arity 1 or 2:

• def execute(params) — receives validated params only
• def execute(params, frame) — receives params and Anubis.Server.Frame.t() (access assigns via frame.assigns)

Return Values

The user's execute function can return:

• {:ok, binary} — returned as text content

• {:ok, map | list} — returned as JSON content

• {:ok, other} — converted to string and returned as text content
• {:error, message} — returned as error content
• {:ok, value, frame} — text/JSON content with updated frame
• {:error, message, frame} — error content with updated frame
• {:noreply, frame} — no content, updated frame
• {:reply, %Response{}, frame} — native Anubis response (passthrough)
• {:error, %Error{}, frame} — native Anubis error (passthrough)