Add dev scripts for mitmproxy debugging and fix JSON-RPC error responses

- Add dev-with-mitm.sh for TUI-based traffic inspection
- Add dev-with-mitmweb.sh for web UI-based traffic inspection
- Fix missing 'id' field in JSON-RPC error responses (required by spec)
- Migrate from zod-to-json-schema to Zod v4's native z.toJSONSchema()

The mitmproxy scripts help developers debug MCP traffic by running
the server through a reverse proxy that intercepts all client requests.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: jerome3o-anthropic

dev-with-mitm.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+# Easy script to run MCP server with mitmproxy intercepting client traffic
+
+echo "🚀 Starting MCP server with mitmproxy..."
+echo ""
+echo "This will:"
+echo "  1. Start your MCP server on port 3232"
+echo "  2. Start mitmproxy reverse proxy on port 8080"
+echo "  3. Intercept all client → server traffic"
+echo ""
+echo "📡 Connect your MCP client to: http://localhost:8080/mcp"
+echo "🔍 View traffic in mitmproxy TUI"
+echo ""
+echo "Press Ctrl+C to stop both processes"
+echo ""
+
+# Trap Ctrl+C to kill both processes
+trap 'kill 0' EXIT
+
+# Start the MCP server in background
+npm run dev &
+SERVER_PID=$!
+
+# Give server time to start
+sleep 3
+
+# Start mitmproxy in reverse proxy mode (foreground so we see the TUI)
+mitmproxy --mode reverse:http://localhost:3232 --listen-port 8080
+
+# This line won't be reached until mitmproxy exits
+wait

dev-with-mitmweb.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+# Easy script to run MCP server with mitmproxy web interface
+
+echo "🚀 Starting MCP server with mitmproxy web UI..."
+echo ""
+echo "This will:"
+echo "  1. Start your MCP server on port 3232"
+echo "  2. Start mitmproxy with web UI on port 8081"
+echo "  3. Proxy client traffic through port 8080"
+echo ""
+echo "📡 Connect your MCP client to: http://localhost:8080/mcp"
+echo "🌐 View traffic in browser at: http://localhost:8081"
+echo ""
+echo "Press Ctrl+C to stop both processes"
+echo ""
+
+# Trap Ctrl+C to kill both processes
+trap 'kill 0' EXIT
+
+# Start the MCP server in background
+npm run dev &
+SERVER_PID=$!
+
+# Give server time to start
+sleep 3
+
+# Start mitmweb in reverse proxy mode
+mitmweb --mode reverse:http://localhost:3232 --listen-port 8080 --web-port 8081
+
+# This line won't be reached until mitmweb exits
+wait

src/modules/mcp/handlers/shttp.ts

@@ -67,6 +67,7 @@ export async function handleStreamableHTTP(req: Request, res: Response) {
       });
       res.status(401).json({
         "jsonrpc": "2.0",
+        "id": null,
         "error": {
           "code": -32002,
           "message": "User ID required"
@@ -87,6 +88,7 @@ export async function handleStreamableHTTP(req: Request, res: Response) {
         });
         res.status(401).json({
           "jsonrpc": "2.0",
+          "id": null,
           "error": {
             "code": -32001,
             "message": "Session not found or access denied"
@@ -148,6 +150,7 @@ export async function handleStreamableHTTP(req: Request, res: Response) {
       });
       res.status(400).json({
         "jsonrpc": "2.0",
+        "id": null,
         "error": {
           "code": -32600,
           "message": "Invalid request method for existing session"
@@ -167,6 +170,7 @@ export async function handleStreamableHTTP(req: Request, res: Response) {
     if (!res.headersSent) {
       res.status(500).json({
         "jsonrpc": "2.0",
+        "id": null,
         "error": {
           "code": -32603,
           "message": "Internal error during request processing"

src/modules/mcp/services/mcp.ts

@@ -19,12 +19,13 @@ import {
   UnsubscribeRequestSchema,
 } from "@modelcontextprotocol/sdk/types.js";
 import { z } from "zod";
-import { zodToJsonSchema } from "zod-to-json-schema";
 
-type ToolInput = {
-  type: "object";
-  properties?: Record<string, unknown>;
-  required?: string[];
+type ToolInput = Tool["inputSchema"];
+
+// Helper to convert Zod schema to JSON schema using Zod v4's native support
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+const toJsonSchema = (schema: z.ZodType<any>): ToolInput => {
+  return z.toJSONSchema(schema) as ToolInput;
 };
 
 /* Input schemas for tools implemented in this server */
@@ -413,40 +414,40 @@ export const createMcpServer = (): McpServerWrapper => {
       {
         name: ToolName.ECHO,
         description: "Echoes back the input",
-        inputSchema: zodToJsonSchema(EchoSchema) as ToolInput,
+        inputSchema: toJsonSchema(EchoSchema),
       },
       {
         name: ToolName.ADD,
         description: "Adds two numbers",
-        inputSchema: zodToJsonSchema(AddSchema) as ToolInput,
+        inputSchema: toJsonSchema(AddSchema),
       },
       {
         name: ToolName.LONG_RUNNING_OPERATION,
         description:
           "Demonstrates a long running operation with progress updates",
-        inputSchema: zodToJsonSchema(LongRunningOperationSchema) as ToolInput,
+        inputSchema: toJsonSchema(LongRunningOperationSchema),
       },
       {
         name: ToolName.SAMPLE_LLM,
         description: "Samples from an LLM using MCP's sampling feature",
-        inputSchema: zodToJsonSchema(SampleLLMSchema) as ToolInput,
+        inputSchema: toJsonSchema(SampleLLMSchema),
       },
       {
         name: ToolName.GET_TINY_IMAGE,
         description: "Returns the MCP_TINY_IMAGE",
-        inputSchema: zodToJsonSchema(GetTinyImageSchema) as ToolInput,
+        inputSchema: toJsonSchema(GetTinyImageSchema),
       },
       {
         name: ToolName.ANNOTATED_MESSAGE,
         description:
           "Demonstrates how annotations can be used to provide metadata about content",
-        inputSchema: zodToJsonSchema(AnnotatedMessageSchema) as ToolInput,
+        inputSchema: toJsonSchema(AnnotatedMessageSchema),
       },
       {
         name: ToolName.GET_RESOURCE_REFERENCE,
         description:
           "Returns a resource reference that can be used by MCP clients",
-        inputSchema: zodToJsonSchema(GetResourceReferenceSchema) as ToolInput,
+        inputSchema: toJsonSchema(GetResourceReferenceSchema),
       },
       {
         name: ToolName.ELICIT_INPUTS,
@@ -524,9 +525,12 @@ export const createMcpServer = (): McpServerWrapper => {
         ToolName.SAMPLE_LLM,
         maxTokens
       );
+      const contentArray = Array.isArray(result.content) ? result.content : [result.content];
+      const firstContent = contentArray[0];
+      const textContent = firstContent && "text" in firstContent ? firstContent.text : JSON.stringify(result.content);
       return {
         content: [
-          { type: "text", text: `LLM sampling result: ${result.content.text}` },
+          { type: "text", text: `LLM sampling result: ${textContent}` },
         ],
       };
     }