Defines the behaviour for MCP resources.

Resources represent data that can be read by the client, such as files, documents, or any other content. Each resource is identified by a URI and can provide content in various formats.

Example

defmodule MyServer.Resources.Documentation do
  @behaviour Hermes.Server.Behaviour.Resource

  alias Hermes.Server.Frame

  @impl true
  def uri, do: "file:///docs/readme.md"

  @impl true
  def name, do: "Project README"

  @impl true
  def description, do: "The main documentation for this project"

  @impl true
  def mime_type, do: "text/markdown"

  @impl true
  def read(_params, frame) do
    case File.read("README.md") do
      {:ok, content} -> 
        # Can track access in frame
        new_frame = Frame.assign(frame, :last_resource_access, DateTime.utc_now())
        {:ok, content, new_frame}

      {:error, reason} -> 
        {:error, "Failed to read README: #{inspect(reason)}"}
    end
  end
end

Example with dynamic content

defmodule MyServer.Resources.SystemStatus do
  @behaviour Hermes.Server.Behaviour.Resource

  @impl true
  def uri, do: "system://status"

  @impl true
  def name, do: "System Status"

  @impl true
  def description, do: "Current system status and metrics"

  @impl true
  def mime_type, do: "application/json"

  @impl true
  def read(_params, frame) do
    status = %{
      uptime: System.uptime(),
      memory: :erlang.memory(),
      user_id: frame.assigns[:user_id],
      timestamp: DateTime.utc_now()
    }

    {:ok, Jason.encode!(status), frame}
  end
end