fix(mcp): strip outputSchema from proxied tool definitions

MCP SDK 1.28.0 clients validate structuredContent against outputSchema
via AJV. When the proxy forwards tool definitions with outputSchema,
downstream clients reject valid upstream responses. Strip outputSchema
so the proxy stays transparent.

Author: tenequm

packages/x402-proxy/package.json

@@ -1,7 +1,7 @@
 {
   "name": "x402-proxy",
   "private": true,
-  "version": "0.10.10",
+  "version": "0.10.11",
   "description": "curl for x402 paid APIs. Auto-pays any endpoint on Base, Solana, and Tempo.",
   "type": "module",
   "sideEffects": false,

packages/x402-proxy/src/commands/mcp.test.ts

@@ -8,7 +8,7 @@ import {
 } from "./mcp.js";
 
 describe("cloneTool", () => {
-  it("preserves outputSchema and extra tool metadata", () => {
+  it("strips outputSchema and preserves other tool metadata", () => {
     const tool = {
       name: "surf_web_search",
       title: "Web Search",
@@ -23,7 +23,16 @@ describe("cloneTool", () => {
       execution: { taskSupport: "optional" },
     };
 
-    expect(cloneTool(tool)).toEqual(tool);
+    const cloned = cloneTool(tool);
+    expect(cloned).not.toHaveProperty("outputSchema");
+    expect(cloned).toEqual({
+      name: "surf_web_search",
+      title: "Web Search",
+      description: "Search the web",
+      inputSchema: { type: "object" },
+      annotations: { readOnlyHint: true },
+      execution: { taskSupport: "optional" },
+    });
   });
 });
 

packages/x402-proxy/src/commands/mcp.ts

@@ -56,7 +56,10 @@ const X402_PAYMENT_META_KEY = "x402/payment";
 const X402_PAYMENT_RESPONSE_META_KEY = "x402/payment-response";
 
 export function cloneTool(tool: ToolDefinition): ToolDefinition {
-  return { ...tool };
+  // Strip outputSchema so downstream clients don't attempt AJV validation
+  // of structuredContent — the proxy passes data through as-is.
+  const { outputSchema: _, ...rest } = tool as ToolDefinition & { outputSchema?: unknown };
+  return rest as ToolDefinition;
 }
 
 export function cloneResource(resource: ResourceDefinition): ResourceDefinition {