docs(mcp): replace @All with explicit POST/GET/DELETE and add OpenAPI descriptions

- restrict endpoint to spec-mandated HTTP methods only
- POST: JSON-RPC messages, responds with application/json or SSE
- GET: opens persistent SSE stream for server-to-client push
- DELETE: optional client-initiated session termination via Mcp-Session-Id

src/mcp/mcp.controller.ts

@@ -1,13 +1,53 @@
-import { All, Controller, Req, Res } from '@nestjs/common';
+import { Controller, Delete, Get, Post, Req, Res } from '@nestjs/common';
+import { ApiOperation, ApiResponse, ApiTags } from '@nestjs/swagger';
 import type { Request, Response } from 'express';
 import { McpService } from './mcp.service';
 
+@ApiTags('mcp')
 @Controller('mcp')
 export class McpController {
   constructor(private readonly mcpService: McpService) {}
 
-  @All()
-  handle(@Req() req: Request, @Res() res: Response): Promise<void> {
+  @Post()
+  @ApiOperation({
+    summary: 'Send JSON-RPC message',
+    description:
+      'Accepts a JSON-RPC request, notification, or response. ' +
+      'Returns either `application/json` for a single response or ' +
+      '`text/event-stream` (SSE) when the server streams multiple messages.',
+  })
+  @ApiResponse({ status: 200, description: 'JSON-RPC response (application/json or text/event-stream)' })
+  @ApiResponse({ status: 202, description: 'Accepted — input was a notification or response only' })
+  @ApiResponse({ status: 400, description: 'Bad Request — malformed JSON-RPC payload' })
+  post(@Req() req: Request, @Res() res: Response): Promise<void> {
+    return this.mcpService.handle(req, res);
+  }
+
+  @Get()
+  @ApiOperation({
+    summary: 'Open server-sent event stream',
+    description:
+      'Opens a persistent SSE stream so the server can push JSON-RPC requests and ' +
+      'notifications to the client without a prior POST. ' +
+      'Requires `Accept: text/event-stream`. Pass `Last-Event-ID` to resume a broken stream.',
+  })
+  @ApiResponse({ status: 200, description: 'SSE stream (text/event-stream)' })
+  @ApiResponse({ status: 405, description: 'Method Not Allowed — server does not offer an SSE stream' })
+  get(@Req() req: Request, @Res() res: Response): Promise<void> {
+    return this.mcpService.handle(req, res);
+  }
+
+  @Delete()
+  @ApiOperation({
+    summary: 'Terminate session',
+    description:
+      'Explicitly terminates a session identified by the `Mcp-Session-Id` header. ' +
+      'The server may return 405 if it does not support client-initiated session termination.',
+  })
+  @ApiResponse({ status: 200, description: 'Session terminated' })
+  @ApiResponse({ status: 404, description: 'Session not found' })
+  @ApiResponse({ status: 405, description: 'Method Not Allowed — server does not support session termination' })
+  delete(@Req() req: Request, @Res() res: Response): Promise<void> {
     return this.mcpService.handle(req, res);
   }
 }