diff --git a/CHANGELOG.md b/CHANGELOG.md
index f5e7d18f4b9..b5c525c707f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -70,6 +70,7 @@ Docs: https://docs.openclaw.ai
 - Sessions: honor configured `session.maintenance` settings during load-time maintenance instead of falling back to default entry caps. Fixes #71356. Thanks @comolago.
 - Browser/sandbox: pass the resolved `browser.ssrfPolicy` into sandbox browser bridges and refresh cached bridges when the effective policy changes, so sandboxed browser navigation honors private-network opt-ins. Fixes #45153 and #57055. Thanks @jzakirov, @zuoanCo, and @kybrcore.
 - Browser/proxy: keep Gateway/provider proxy environment variables from proxying the OpenClaw-managed browser, so `HTTP_PROXY` and `HTTPS_PROXY` no longer block ordinary browser navigation. Fixes #71358. Thanks @Sanjays2402.
+- Agents/MCP: validate draft-2020-12 MCP tool output schemas with a draft-aware bundle-MCP client validator, so external MCP servers no longer fail catalog/tool execution with missing schema refs. Fixes #68772 and #70196. Thanks @mwiesen.
 - Dashboard/Windows: open Control UI and OAuth URLs through the system URL handler without `cmd.exe` parsing or PATH-based `rundll32` lookup, and reject non-HTTP browser-open inputs. Fixes #71098. Thanks @Sanjays2402.
 - Config/doctor: reject legacy `secretref-env:<ENV_VAR>` marker strings on SecretRef credential paths and migrate valid markers to structured env SecretRefs with `openclaw doctor --fix`. Fixes #51794. Thanks @halointellicore.
 - Providers/OpenAI: separate API-key and Codex sign-in onboarding groups, and avoid replaying stale OpenAI Responses reasoning blocks after a model route switch.
diff --git a/src/agents/pi-bundle-mcp-runtime.test.ts b/src/agents/pi-bundle-mcp-runtime.test.ts
index 456236ac78d..2f2eac1a6bb 100644
--- a/src/agents/pi-bundle-mcp-runtime.test.ts
+++ b/src/agents/pi-bundle-mcp-runtime.test.ts
@@ -1,4 +1,5 @@
 import { afterEach, describe, expect, it, vi } from "vitest";
+import { createBundleMcpJsonSchemaValidator } from "./pi-bundle-mcp-runtime.js";
 import { cleanupBundleMcpHarness } from "./pi-bundle-mcp-test-harness.js";
 import {
   __testing,
@@ -69,6 +70,25 @@ afterEach(async () => {
 });
 
 describe("session MCP runtime", () => {
+  it("accepts draft-2020-12 tool output schemas from external MCP catalogs", () => {
+    const validator = createBundleMcpJsonSchemaValidator().getValidator<{ url: string }>({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      type: "object",
+      properties: {
+        url: { type: "string" },
+      },
+      required: ["url"],
+      additionalProperties: false,
+    });
+
+    expect(validator({ url: "https://example.com" })).toEqual({
+      valid: true,
+      data: { url: "https://example.com" },
+      errorMessage: undefined,
+    });
+    expect(validator({ url: 42 }).valid).toBe(false);
+  });
+
   it("keeps colliding sanitized tool definitions stable across catalog order changes", async () => {
     const catalogA = [
       { toolName: "alpha?", description: "question" },
diff --git a/src/agents/pi-bundle-mcp-runtime.ts b/src/agents/pi-bundle-mcp-runtime.ts
index f525ff4da6d..801a4039185 100644
--- a/src/agents/pi-bundle-mcp-runtime.ts
+++ b/src/agents/pi-bundle-mcp-runtime.ts
@@ -1,8 +1,16 @@
 import crypto from "node:crypto";
+import { createRequire } from "node:module";
 import { Client } from "@modelcontextprotocol/sdk/client/index.js";
 import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js";
 import type { Transport } from "@modelcontextprotocol/sdk/shared/transport.js";
 import type { CallToolResult } from "@modelcontextprotocol/sdk/types.js";
+import { AjvJsonSchemaValidator } from "@modelcontextprotocol/sdk/validation/ajv-provider.js";
+import type {
+  JsonSchemaType,
+  JsonSchemaValidator,
+  jsonSchemaValidator,
+} from "@modelcontextprotocol/sdk/validation/types.js";
+import type { ErrorObject, ValidateFunction } from "ajv";
 import type { OpenClawConfig } from "../config/types.openclaw.js";
 import { logWarn } from "../logger.js";
 import { resolveGlobalSingleton } from "../shared/global-singleton.js";
@@ -34,7 +42,53 @@ type CreateSessionMcpRuntime = (
   params: Parameters<typeof createSessionMcpRuntime>[0] & { configFingerprint?: string },
 ) => SessionMcpRuntime;
 
+const require = createRequire(import.meta.url);
 const SESSION_MCP_RUNTIME_MANAGER_KEY = Symbol.for("openclaw.sessionMcpRuntimeManager");
+const DRAFT_2020_12_SCHEMA = "https://json-schema.org/draft/2020-12/schema";
+
+type Ajv2020Like = {
+  compile: (schema: JsonSchemaType) => ValidateFunction;
+  errorsText: (errors?: ErrorObject[] | null) => string;
+};
+
+function isDraft202012Schema(schema: JsonSchemaType): boolean {
+  return (schema as { $schema?: unknown }).$schema === DRAFT_2020_12_SCHEMA;
+}
+
+export function createBundleMcpJsonSchemaValidator(): jsonSchemaValidator {
+  const defaultValidator = new AjvJsonSchemaValidator();
+  const Ajv2020Ctor = require("ajv/dist/2020") as new (opts?: object) => Ajv2020Like;
+  const ajv2020 = new Ajv2020Ctor({
+    strict: false,
+    validateFormats: false,
+    validateSchema: false,
+    allErrors: true,
+  });
+
+  return {
+    getValidator<T>(schema: JsonSchemaType): JsonSchemaValidator<T> {
+      if (!isDraft202012Schema(schema)) {
+        return defaultValidator.getValidator<T>(schema);
+      }
+      const ajvValidator = ajv2020.compile(schema);
+      return (input: unknown) => {
+        const valid = ajvValidator(input);
+        if (valid) {
+          return {
+            valid: true,
+            data: input as T,
+            errorMessage: undefined,
+          };
+        }
+        return {
+          valid: false,
+          data: undefined,
+          errorMessage: ajv2020.errorsText(ajvValidator.errors),
+        };
+      };
+    },
+  };
+}
 
 function connectWithTimeout(
   client: Client,
@@ -178,7 +232,9 @@ export function createSessionMcpRuntime(params: {
               name: "openclaw-bundle-mcp",
               version: "0.0.0",
             },
-            {},
+            {
+              jsonSchemaValidator: createBundleMcpJsonSchemaValidator(),
+            },
           );
           const session: BundleMcpSession = {
             serverName,