This project provides a dynamic, configurable MCP (Model-Context-Protocol) server written in Go. Its primary purpose is to wrap existing HTTP APIs and expose them as MCP tools without requiring any changes to the Go source code. New tools can be added and configured by simply editing the config.json file.

• Declarative Tool Creation: Define tools entirely within a config.json file.
• No Go Programming Needed: Add new tools by simply editing the configuration.
• HTTP Method Support: Works with GET, POST, PUT, and other standard HTTP methods.
• Flexible Headers: Add any number of custom HTTP headers, perfect for API keys, bearer tokens, or any other authentication scheme.
• Powerful Response Mapping: A flexible system to parse complex JSON responses (including nested objects and arrays) into clean, human-readable output for the model.

The server acts as a bridge between an AI model and any external HTTP API. When the model calls a tool, the server looks up the tool's definition in config.json, constructs the appropriate HTTP request, sends it to the target API, and then parses the response according to the mapping rules before returning a formatted result to the model.

sequenceDiagram
    participant Model as AI Model
    participant MCPServer as hyancie-mcp Server
    participant Config as config.json
    participant API as External HTTP API

    Model->>+MCPServer: Call tool('get_weather_cn', {city: 'Beijing'})
    MCPServer->>+Config: Read tool definition
    Config-->>-MCPServer: Return tool details (URL, auth, etc.)
    MCPServer->>+API: Make HTTP GET request to api.example.com/weather?city=Beijing
    API-->>-MCPServer: Return JSON weather data
    MCPServer->>+Config: Read output_mapping rules
    Config-->>-MCPServer: Return mapping rules
    MCPServer->>-Model: Return formatted result: "温度:22|湿度:50|..."

• Go 1.18 or higher.

To build the executable, run the following command from the project root directory:

go build -o hyancie-mcp.exe ./cmd/hyancie

The server can run in two transport modes: stdio (for local communication with a parent process) or sse (to expose an HTTP server with Server-Sent Events).

Stdio Mode (Default):

./hyancie-mcp.exe

SSE Mode:

You can specify the address for the SSE server.

./hyancie-mcp.exe -t sse --sse-address 0.0.0.0:8001 --sse-base-url https://xx.com

This file is the heart of the server. It defines the server's identity and the tools it provides.

Important: The config.json file must be located in the same directory as the compiled executable (e.g., hyancie-mcp.exe). The server will look for it there at startup.

• server_name (string): The name of your MCP server.
• server_version (string): The version of your server.
• sse_address (string): The default address for the SSE server.
• mcp_tools (array): An array of tool definition objects.

Each object in the mcp_tools array defines a single tool.

• tool_name (string, required): The unique identifier for the tool (e.g., get_weather_cn).
• description (string, required): A clear description of what the tool does. This is what the AI model uses to decide when to use the tool.
• input_schema (object, required): Defines the tool's arguments using JSON Schema.
  • type: Should be "object".
  • properties: An object where each key is an argument name and the value is a schema defining its type and description. You can also add a default key here to provide a fallback value if the model doesn't supply one for a non-required argument.
  • required: An array of strings listing the mandatory arguments.
• request (object, required): Configures the outgoing HTTP request.
  • method (string): The HTTP method (e.g., "GET", "POST").
  • url (string): The API endpoint. For GET requests, use {placeholder} syntax to insert arguments into the URL. For POST/PUT, the arguments from input_schema are sent as the JSON request body.
• headers (array, optional): An array of objects to define custom HTTP headers to be sent with the request. This is the standard way to handle authentication (e.g., API keys, bearer tokens).
  • Each object in the array must have a name (string) and a value (string).
• output_mapping (array, required): A powerful system for parsing the JSON response from the API into a flat, text-based format for the model.
  • json_key (string): The key to extract from the JSON response. Supports dot notation for nested objects (main.temp) and array indexing (weather[0].description).
  • description (string): A human-readable label for the extracted value (e.g., "Temperature").
  • type (string): Can be "primitive" or "array".
    • primitive: For extracting simple values like strings, numbers, or booleans.
    • array: For processing a list of objects.
  • limit (integer, optional): Used with type: "array" to restrict the number of items processed from the array.
  • items (array, optional): Used with type: "array". This is a nested output_mapping that defines how to process each object within the array.

This tool fetches weather data. The city argument is inserted into the URL, and a custom header is added for authentication. The output mapping extracts simple, nested values from the JSON response.

Config:

{
  "tool_name": "get_weather_cn",
  "description": "根据城市名称获取实时天气信息。",
  "request": {
    "method": "GET",
    "url": "https://api.example.com/weather?city={city}&unit=metric"
  },
  "headers": [
    {
      "name": "X-Api-Key",
      "value": "your-secret-api-key-goes-here"
    }
  ],
  "input_schema": { ... },
  "output_mapping": [
    { "json_key": "main.temp", "description": "温度", "type": "primitive" },
    { "json_key": "main.humidity", "description": "湿度", "type": "primitive" },
    { "json_key": "weather[0].description", "description": "天气状况", "type": "primitive" }
  ]
}

Result: 温度:22|湿度:50|天气状况:clear sky

This tool performs a search and processes a list of results. The output_mapping for the results key is of type array. It iterates through the top 3 items, and for each item, it applies the nested items mapping to extract the title, url, and content.

Config:

{
  "tool_name": "food-info-search",
  "description": "食品网页搜索工具。提取并格式化前3个搜索结果。",
  "request": { ... },
  "input_schema": { ... },
  "output_mapping": [
    {
      "json_key": "results",
      "type": "array",
      "description": "搜索结果",
      "limit": 3,
      "items": [
        { "json_key": "title", "description": "标题", "type": "primitive" },
        { "json_key": "url", "description": "链接", "type": "primitive" },
        { "json_key": "content", "description": "简介", "type": "primitive" }
      ]
    }
  ]
}

Result: 搜索结果:[项1:{标题:..., 链接:...} | 项2:{标题:..., 链接:...} | 项3:{标题:..., 链接:...}]

A sample Python client is available in the client/ directory. Please see the client/README.md for instructions on how to use it.

This project is licensed under the GPLv2.0 License.