add(mcp): Add MCP Server name to ToolCallEvent OTel logging (#7829)

Co-authored-by: Shnatu <snatu@google.com>
Co-authored-by: owenofbrien <86964623+owenofbrien@users.noreply.github.com>
Co-authored-by: Abhi <43648792+abhipatel12@users.noreply.github.com>

packages/core/src/telemetry/clearcut-logger/clearcut-logger.ts

@@ -477,6 +477,10 @@ export class ClearcutLogger {
         gemini_cli_key: EventMetadataKey.GEMINI_CLI_TOOL_CALL_CONTENT_LENGTH,
         value: JSON.stringify(event.content_length),
       },
+      {
+        gemini_cli_key: EventMetadataKey.GEMINI_CLI_TOOL_CALL_MCP_SERVER_NAME,
+        value: JSON.stringify(event.mcp_server_name),
+      },
     ];
 
     if (event.metadata) {

packages/core/src/telemetry/clearcut-logger/event-metadata-key.ts

@@ -50,6 +50,9 @@ export enum EventMetadataKey {
   // Logs whether the session was configured to respect gitignore files.
   GEMINI_CLI_START_SESSION_RESPECT_GITIGNORE = 12,
 
+  // Logs the output format of the session.
+  GEMINI_CLI_START_SESSION_OUTPUT_FORMAT = 94,
+
   // ==========================================================================
   // User Prompt Event Keys
   // ===========================================================================
@@ -64,6 +67,9 @@ export enum EventMetadataKey {
   // Logs the function name.
   GEMINI_CLI_TOOL_CALL_NAME = 14,
 
+  // Logs the MCP server name.
+  GEMINI_CLI_TOOL_CALL_MCP_SERVER_NAME = 95,
+
   // Logs the user's decision about how to handle the tool call.
   GEMINI_CLI_TOOL_CALL_DECISION = 15,
 

packages/core/src/telemetry/loggers.test.ts

@@ -76,7 +76,11 @@ import * as metrics from './metrics.js';
 import { FileOperation } from './metrics.js';
 import * as sdk from './sdk.js';
 import { vi, describe, beforeEach, it, expect, afterEach } from 'vitest';
-import type { GenerateContentResponseUsageMetadata } from '@google/genai';
+import type {
+  CallableTool,
+  GenerateContentResponseUsageMetadata,
+} from '@google/genai';
+import { DiscoveredMCPTool } from '../tools/mcp-tool.js';
 import * as uiTelemetry from './uiTelemetry.js';
 import { makeFakeConfig } from '../test-utils/config.js';
 import { ClearcutLogger } from './clearcut-logger/clearcut-logger.js';
@@ -930,6 +934,75 @@ describe('loggers', () => {
         'event.timestamp': '2025-01-01T00:00:00.000Z',
       });
     });
+
+    it('should log a tool call with mcp_server_name for MCP tools', () => {
+      const mockMcpTool = new DiscoveredMCPTool(
+        {} as CallableTool,
+        'mock_mcp_server',
+        'mock_mcp_tool',
+        'tool description',
+        {
+          type: 'object',
+          properties: {
+            arg1: { type: 'string' },
+            arg2: { type: 'number' },
+          },
+          required: ['arg1', 'arg2'],
+        },
+      );
+
+      const call: CompletedToolCall = {
+        status: 'success',
+        request: {
+          name: 'mock_mcp_tool',
+          args: { arg1: 'value1', arg2: 2 },
+          callId: 'test-call-id',
+          isClientInitiated: true,
+          prompt_id: 'prompt-id',
+        },
+        response: {
+          callId: 'test-call-id',
+          responseParts: [{ text: 'test-response' }],
+          resultDisplay: undefined,
+          error: undefined,
+          errorType: undefined,
+        },
+        tool: mockMcpTool,
+        invocation: {} as AnyToolInvocation,
+        durationMs: 100,
+      };
+      const event = new ToolCallEvent(call);
+
+      logToolCall(mockConfig, event);
+
+      expect(mockLogger.emit).toHaveBeenCalledWith({
+        body: 'Tool call: mock_mcp_tool. Success: true. Duration: 100ms.',
+        attributes: {
+          'session.id': 'test-session-id',
+          'user.email': 'test-user@example.com',
+          'event.name': EVENT_TOOL_CALL,
+          'event.timestamp': '2025-01-01T00:00:00.000Z',
+          function_name: 'mock_mcp_tool',
+          function_args: JSON.stringify(
+            {
+              arg1: 'value1',
+              arg2: 2,
+            },
+            null,
+            2,
+          ),
+          duration_ms: 100,
+          success: true,
+          prompt_id: 'prompt-id',
+          tool_type: 'mcp',
+          mcp_server_name: 'mock_mcp_server',
+          decision: undefined,
+          error: undefined,
+          error_type: undefined,
+          metadata: undefined,
+        },
+      });
+    });
   });
 
   describe('logMalformedJsonResponse', () => {

packages/core/src/telemetry/types.ts

@@ -137,6 +137,7 @@ export class ToolCallEvent implements BaseTelemetryEvent {
   prompt_id: string;
   tool_type: 'native' | 'mcp';
   content_length?: number;
+  mcp_server_name?: string;
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   metadata?: { [key: string]: any };
 
@@ -153,11 +154,16 @@ export class ToolCallEvent implements BaseTelemetryEvent {
     this.error = call.response.error?.message;
     this.error_type = call.response.errorType;
     this.prompt_id = call.request.prompt_id;
-    this.tool_type =
-      typeof call.tool !== 'undefined' && call.tool instanceof DiscoveredMCPTool
-        ? 'mcp'
-        : 'native';
     this.content_length = call.response.contentLength;
+    if (
+      typeof call.tool !== 'undefined' &&
+      call.tool instanceof DiscoveredMCPTool
+    ) {
+      this.tool_type = 'mcp';
+      this.mcp_server_name = call.tool.serverName;
+    } else {
+      this.tool_type = 'native';
+    }
 
     if (
       call.status === 'success' &&