feat(core): add tools to list and read MCP resources (#25395)

integration-tests/mcp-list-resources.responses

@@ -0,0 +1,2 @@
+{"method":"generateContentStream","response":[{"candidates":[{"content":{"parts":[{"functionCall":{"name":"list_mcp_resources","args":{}}}],"role":"model"},"finishReason":"STOP","index":0}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":10,"totalTokenCount":20}}]}
+{"method":"generateContentStream","response":[{"candidates":[{"content":{"parts":[{"text":"Here are the resources: test://resource1"}],"role":"model"},"finishReason":"STOP","index":0}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":10,"totalTokenCount":20}}]}

integration-tests/mcp-read-resource.responses

@@ -0,0 +1,2 @@
+{"method":"generateContentStream","response":[{"candidates":[{"content":{"parts":[{"functionCall":{"name":"read_mcp_resource","args":{"uri":"test://resource1"}}}],"role":"model"},"finishReason":"STOP","index":0}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":10,"totalTokenCount":20}}]}
+{"method":"generateContentStream","response":[{"candidates":[{"content":{"parts":[{"text":"The content is: content of resource 1"}],"role":"model"},"finishReason":"STOP","index":0}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":10,"totalTokenCount":20}}]}

integration-tests/mcp-resources.responses

@@ -0,0 +1,4 @@
+{"method":"generateContentStream","response":[{"candidates":[{"content":{"parts":[{"functionCall":{"name":"list_mcp_resources","args":{}}}],"role":"model"},"finishReason":"STOP","index":0}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":10,"totalTokenCount":20}}]}
+{"method":"generateContentStream","response":[{"candidates":[{"content":{"parts":[{"text":"Here are the resources: test://resource1"}],"role":"model"},"finishReason":"STOP","index":0}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":10,"totalTokenCount":20}}]}
+{"method":"generateContentStream","response":[{"candidates":[{"content":{"parts":[{"functionCall":{"name":"read_mcp_resource","args":{"uri":"test://resource1"}}}],"role":"model"},"finishReason":"STOP","index":0}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":10,"totalTokenCount":20}}]}
+{"method":"generateContentStream","response":[{"candidates":[{"content":{"parts":[{"text":"The content is: content of resource 1"}],"role":"model"},"finishReason":"STOP","index":0}],"usageMetadata":{"promptTokenCount":10,"candidatesTokenCount":10,"totalTokenCount":20}}]}

integration-tests/mcp-resources.test.ts

@@ -0,0 +1,178 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
+import { TestRig } from './test-helper.js';
+import { join, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import fs from 'node:fs';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+describe('mcp-resources-integration', () => {
+  let rig: TestRig;
+
+  beforeEach(() => {
+    rig = new TestRig();
+  });
+
+  afterEach(async () => await rig.cleanup());
+
+  it('should list mcp resources', async () => {
+    await rig.setup('mcp-list-resources-test', {
+      settings: {
+        model: {
+          name: 'gemini-3-flash-preview',
+        },
+      },
+      fakeResponsesPath: join(__dirname, 'mcp-list-resources.responses'),
+    });
+
+    // Workaround for ProjectRegistry save issue
+    const userGeminiDir = join(rig.homeDir!, '.gemini');
+    fs.writeFileSync(join(userGeminiDir, 'projects.json'), '{"projects":{}}');
+
+    // Add a dummy server to get setup done
+    rig.addTestMcpServer('resource-server', {
+      name: 'resource-server',
+      tools: [],
+    });
+
+    // Overwrite the script with resource support
+    const scriptPath = join(rig.testDir!, 'test-mcp-resource-server.mjs');
+    const scriptContent = `
+import { Server } from '@modelcontextprotocol/sdk/server/index.js';
+import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
+import {
+  ListResourcesRequestSchema,
+} from '@modelcontextprotocol/sdk/types.js';
+
+const server = new Server(
+  {
+    name: 'resource-server',
+    version: '1.0.0',
+  },
+  {
+    capabilities: {
+      resources: {},
+    },
+  },
+);
+
+server.setRequestHandler(ListResourcesRequestSchema, async () => {
+  return {
+    resources: [
+      {
+        uri: 'test://resource1',
+        name: 'Resource 1',
+        mimeType: 'text/plain',
+        description: 'A test resource',
+      }
+    ],
+  };
+});
+
+const transport = new StdioServerTransport();
+await server.connect(transport);
+`;
+    fs.writeFileSync(scriptPath, scriptContent);
+
+    const output = await rig.run({
+      args: 'List all available MCP resources.',
+      env: { GEMINI_API_KEY: 'dummy' },
+    });
+
+    const foundCall = await rig.waitForToolCall('list_mcp_resources');
+    expect(foundCall).toBeTruthy();
+    expect(output).toContain('test://resource1');
+  }, 60000);
+
+  it('should read mcp resource', async () => {
+    await rig.setup('mcp-read-resource-test', {
+      settings: {
+        model: {
+          name: 'gemini-3-flash-preview',
+        },
+      },
+      fakeResponsesPath: join(__dirname, 'mcp-read-resource.responses'),
+    });
+
+    // Workaround for ProjectRegistry save issue
+    const userGeminiDir = join(rig.homeDir!, '.gemini');
+    fs.writeFileSync(join(userGeminiDir, 'projects.json'), '{"projects":{}}');
+
+    // Add a dummy server to get setup done
+    rig.addTestMcpServer('resource-server', {
+      name: 'resource-server',
+      tools: [],
+    });
+
+    // Overwrite the script with resource support
+    const scriptPath = join(rig.testDir!, 'test-mcp-resource-server.mjs');
+    const scriptContent = `
+import { Server } from '@modelcontextprotocol/sdk/server/index.js';
+import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
+import {
+  ListResourcesRequestSchema,
+  ReadResourceRequestSchema,
+} from '@modelcontextprotocol/sdk/types.js';
+
+const server = new Server(
+  {
+    name: 'resource-server',
+    version: '1.0.0',
+  },
+  {
+    capabilities: {
+      resources: {},
+    },
+  },
+);
+
+// Need to provide list resources so the tool is active!
+server.setRequestHandler(ListResourcesRequestSchema, async () => {
+  return {
+    resources: [
+      {
+        uri: 'test://resource1',
+        name: 'Resource 1',
+        mimeType: 'text/plain',
+        description: 'A test resource',
+      }
+    ],
+  };
+});
+
+server.setRequestHandler(ReadResourceRequestSchema, async (request) => {
+  if (request.params.uri === 'test://resource1') {
+    return {
+      contents: [
+        {
+          uri: 'test://resource1',
+          mimeType: 'text/plain',
+          text: 'This is the content of resource 1',
+        }
+      ],
+    };
+  }
+  throw new Error('Resource not found');
+});
+
+const transport = new StdioServerTransport();
+await server.connect(transport);
+`;
+    fs.writeFileSync(scriptPath, scriptContent);
+
+    const output = await rig.run({
+      args: 'Read the MCP resource test://resource1.',
+      env: { GEMINI_API_KEY: 'dummy' },
+    });
+
+    const foundCall = await rig.waitForToolCall('read_mcp_resource');
+    expect(foundCall).toBeTruthy();
+    expect(output).toContain('content of resource 1');
+  }, 60000);
+});