一个最小化的Elixir MCP（模型上下文协议）服务器。

布置

1.初始化会话存储

将会话存储初始化添加到你的应用程序 start/2：

你可以通过实现 EMCP.SessionStore 行为来使用自定义会话存储。

2.定义服务器

3.登上运输车

把StreamableHTTP传输添加到你的Phoenix路由器上。把它挂载在任何管道之外，因为EMCP本身负责内容协商：

4.在服务器上添加工具

提示

提示词是可重复使用的模板，返回结构化消息：

资源

资源暴露客户端可读取的数据。静态资源有固定的URI：

资源模板使用URI模式，使客户端可以请求动态内容：

当客户端调用resources/read时，服务器首先尝试对静态资源进行精确的URI匹配。如果没有匹配，则按顺序尝试每个资源模板，直到其中一个处理完URI。

起源验证

为了防止DNS重绑攻击，你可以在传输上启用起源验证。启用后，只有与允许列表匹配的Origin头请求才会被接受。没有Origin头的请求（例如来自CLI工具）始终被允许。

EMCP

A minimal Elixir MCP (Model Context Protocol) server.

Setup

1. Initialize the session store

Add the session store initialization to your application’s start/2:

defmodule MyApp.Application do
  use Application

  def start(_type, _args) do
    EMCP.SessionStore.ETS.init()

    children = [
      # ...
    ]

    Supervisor.start_link(children, strategy: :one_for_one)
  end
end

You can use a custom session store by implementing the EMCP.SessionStore behaviour.

2. Define a server

defmodule MyApp.MCPServer do
  use EMCP.Server,
    name: "my-app",
    version: "1.0.0",
    tools: [MyApp.Tools.Echo],
    prompts: [MyApp.Prompts.CodeReview],
    resources: [MyApp.Resources.Readme],
    resource_templates: [MyApp.ResourceTemplates.UserProfile],
    # You can optionally add these meta fields as well:
    title: "My App",
    description: "MCP server for My App",
    instructions: "Use the tools to interact with My App.",
end

3. Mount the transport

Add the StreamableHTTP transport to your Phoenix router. Mount it outside any pipeline since EMCP handles content negotiation itself:

scope "/mcp" do
  forward "/", EMCP.Transport.StreamableHTTP, server: MyApp.MCPServer
end

4. Add tools to your server

defmodule MyApp.Tools.Echo do
  @behaviour EMCP.Tool

  @impl EMCP.Tool
  def name, do: "echo"

  @impl EMCP.Tool
  def description, do: "Echoes back the provided message"

  @impl EMCP.Tool
  def input_schema do
    %{
      type: :object,
      properties: %{
        message: %{type: :string}
      },
      required: [:message]
    }
  end

  @impl EMCP.Tool
  def call(_conn, %{"message" => message}) do
    EMCP.Tool.response([%{"type" => "text", "text" => message}])
  end

  # Return errors with:
  # EMCP.Tool.error("something went wrong")
end

Prompts

Prompts are reusable templates that return structured messages:

defmodule MyApp.Prompts.CodeReview do
  @behaviour EMCP.Prompt

  @impl EMCP.Prompt
  def name, do: "code_review"

  @impl EMCP.Prompt
  def description, do: "Reviews code with optional focus area"

  @impl EMCP.Prompt
  def arguments do
    [
      %{name: "code", description: "The code to review", required: true},
      %{name: "focus", description: "Optional area to focus on"}
    ]
  end

  @impl EMCP.Prompt
  def template(_conn, %{"code" => code} = args) do
    focus = args["focus"]

    user_text =
      if focus,
        do: "Review this code, focusing on #{focus}:\n\n#{code}",
        else: "Review this code:\n\n#{code}"

    %{
      "description" => "Code review prompt",
      "messages" => [
        %{"role" => "user", "content" => %{"type" => "text", "text" => user_text}},
        %{"role" => "assistant", "content" => %{"type" => "text", "text" => "I'll review the code you've provided."}}
      ]
    }
  end
end

Resources

Resources expose data that clients can read. A static resource has a fixed URI: