MCP Server (Streamable HTTP)

MCP server that exposes the Posts & Comments API as tools over Streamable HTTP. No auth on /mcp.

Requires Node 18+ (MCP SDK and Hono depend on it).

Setup

1. Start the main API (Posts server) first, e.g. on port 3000:

   cd .. && MONGO_URI="mongodb://..." npm start
   

2. Install and start the MCP server (default port 3001):

   npm install
   npm start
   

Configuration

• API_BASE_URL – Base URL of the Posts API (default: http://localhost:3000).
• MCP_PORT – Port for this MCP server (default: 3001).

Endpoint

• POST /mcp – MCP Streamable HTTP endpoint (no authentication).
  MCP clients send JSON-RPC here; the server handles initialization and tool calls.

• GET /mcp – Returns 405 Method Not Allowed (stateless server, no SSE session).

Tools (with validation)

All tools call the main API and apply the same validation rules.

Tool	Description	Validation
create_post	Create a post	title ≥5, author ≥3, category ∈ tech/finance/lifestyle, body ≥50
list_posts	List all posts	—
get_post	Get one post by ID	—
update_post	Update a post	Same as create_post
delete_post	Delete a post (and its comments)	—
add_comment	Add comment to a post	text ≥10, commenter required
list_comments	List comments for a post	—

Validation errors (e.g. invalid category, body too short) are returned as tool errors with clear messages. If the API returns 404 (e.g. post not found), the tool returns that as an error.

Flow

1. MCP client sends POST /mcp with JSON-RPC (e.g. initialize, then tools/call).
2. Server uses Streamable HTTP transport (stateless, new server + transport per request).
3. Tool handlers validate arguments (Zod + custom rules), then fetch() the Posts API.
4. API response is returned as the tool result (or an error).