From 1738d407456aec9ab7733374a4709cff6d59d12d Mon Sep 17 00:00:00 2001
From: Jacob MacDonald <jakemac@google.com>
Date: Wed, 20 Aug 2025 13:10:02 -0700
Subject: [PATCH] return the JSON stringified parameters from getDescription
 for MCP tools and Discovered tools (#6655)

---
 packages/core/src/tools/mcp-tool.test.ts      |  9 +++++++++
 packages/core/src/tools/mcp-tool.ts           |  3 ++-
 packages/core/src/tools/tool-registry.test.ts | 10 ++++++++++
 packages/core/src/tools/tool-registry.ts      |  3 ++-
 packages/core/src/tools/tools.ts              |  1 +
 5 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/packages/core/src/tools/mcp-tool.test.ts b/packages/core/src/tools/mcp-tool.test.ts
index 3a8c10c4..d5e4eee8 100644
--- a/packages/core/src/tools/mcp-tool.test.ts
+++ b/packages/core/src/tools/mcp-tool.test.ts
@@ -743,4 +743,13 @@ describe('DiscoveredMCPTool', () => {
       }
     });
   });
+
+  describe('DiscoveredMCPToolInvocation', () => {
+    it('should return the stringified params from getDescription', () => {
+      const params = { param: 'testValue', param2: 'anotherOne' };
+      const invocation = tool.build(params);
+      const description = invocation.getDescription();
+      expect(description).toBe('{"param":"testValue","param2":"anotherOne"}');
+    });
+  });
 });
diff --git a/packages/core/src/tools/mcp-tool.ts b/packages/core/src/tools/mcp-tool.ts
index 64952dd1..baa517f6 100644
--- a/packages/core/src/tools/mcp-tool.ts
+++ b/packages/core/src/tools/mcp-tool.ts
@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+import { safeJsonStringify } from '../utils/safeJsonStringify.js';
 import {
   BaseDeclarativeTool,
   BaseToolInvocation,
@@ -152,7 +153,7 @@ class DiscoveredMCPToolInvocation extends BaseToolInvocation<
   }
 
   getDescription(): string {
-    return this.displayName;
+    return safeJsonStringify(this.params);
   }
 }
 
diff --git a/packages/core/src/tools/tool-registry.test.ts b/packages/core/src/tools/tool-registry.test.ts
index cccf011f..6db60377 100644
--- a/packages/core/src/tools/tool-registry.test.ts
+++ b/packages/core/src/tools/tool-registry.test.ts
@@ -332,4 +332,14 @@ describe('ToolRegistry', () => {
       expect(discoverSpy).toHaveBeenCalled();
     });
   });
+
+  describe('DiscoveredToolInvocation', () => {
+    it('should return the stringified params from getDescription', () => {
+      const tool = new DiscoveredTool(config, 'test-tool', 'A test tool', {});
+      const params = { param: 'testValue' };
+      const invocation = tool.build(params);
+      const description = invocation.getDescription();
+      expect(description).toBe(JSON.stringify(params));
+    });
+  });
 });
diff --git a/packages/core/src/tools/tool-registry.ts b/packages/core/src/tools/tool-registry.ts
index 90531742..7acd778d 100644
--- a/packages/core/src/tools/tool-registry.ts
+++ b/packages/core/src/tools/tool-registry.ts
@@ -20,6 +20,7 @@ import { connectAndDiscover } from './mcp-client.js';
 import { McpClientManager } from './mcp-client-manager.js';
 import { DiscoveredMCPTool } from './mcp-tool.js';
 import { parse } from 'shell-quote';
+import { safeJsonStringify } from '../utils/safeJsonStringify.js';
 
 type ToolParams = Record<string, unknown>;
 
@@ -36,7 +37,7 @@ class DiscoveredToolInvocation extends BaseToolInvocation<
   }
 
   getDescription(): string {
-    return `Calling discovered tool: ${this.toolName}`;
+    return safeJsonStringify(this.params);
   }
 
   async execute(
diff --git a/packages/core/src/tools/tools.ts b/packages/core/src/tools/tools.ts
index 761b670a..64a2e83a 100644
--- a/packages/core/src/tools/tools.ts
+++ b/packages/core/src/tools/tools.ts
@@ -24,6 +24,7 @@ export interface ToolInvocation<
 
   /**
    * Gets a pre-execution description of the tool operation.
+   *
    * @returns A markdown string describing what the tool will do.
    */
   getDescription(): string;