Add MCP Roots support (#5856)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/core/src/tools/mcp-client.ts

@@ -20,6 +20,7 @@ import {
   ListPromptsResultSchema,
   GetPromptResult,
   GetPromptResultSchema,
+  ListRootsRequestSchema,
 } from '@modelcontextprotocol/sdk/types.js';
 import { parse } from 'shell-quote';
 import { AuthProviderType, MCPServerConfig } from '../config/config.js';
@@ -33,6 +34,9 @@ import { MCPOAuthProvider } from '../mcp/oauth-provider.js';
 import { OAuthUtils } from '../mcp/oauth-utils.js';
 import { MCPOAuthTokenStorage } from '../mcp/oauth-token-storage.js';
 import { getErrorMessage } from '../utils/errors.js';
+import { basename } from 'node:path';
+import { pathToFileURL } from 'node:url';
+import { WorkspaceContext } from '../utils/workspaceContext.js';
 
 export const MCP_DEFAULT_TIMEOUT_MSEC = 10 * 60 * 1000; // default to 10 minutes
 
@@ -306,6 +310,7 @@ export async function discoverMcpTools(
   toolRegistry: ToolRegistry,
   promptRegistry: PromptRegistry,
   debugMode: boolean,
+  workspaceContext: WorkspaceContext,
 ): Promise<void> {
   mcpDiscoveryState = MCPDiscoveryState.IN_PROGRESS;
   try {
@@ -319,6 +324,7 @@ export async function discoverMcpTools(
           toolRegistry,
           promptRegistry,
           debugMode,
+          workspaceContext,
         ),
     );
     await Promise.all(discoveryPromises);
@@ -363,6 +369,7 @@ export async function connectAndDiscover(
   toolRegistry: ToolRegistry,
   promptRegistry: PromptRegistry,
   debugMode: boolean,
+  workspaceContext: WorkspaceContext,
 ): Promise<void> {
   updateMCPServerStatus(mcpServerName, MCPServerStatus.CONNECTING);
 
@@ -372,6 +379,7 @@ export async function connectAndDiscover(
       mcpServerName,
       mcpServerConfig,
       debugMode,
+      workspaceContext,
     );
 
     mcpClient.onerror = (error) => {
@@ -655,12 +663,30 @@ export async function connectToMcpServer(
   mcpServerName: string,
   mcpServerConfig: MCPServerConfig,
   debugMode: boolean,
+  workspaceContext: WorkspaceContext,
 ): Promise<Client> {
   const mcpClient = new Client({
     name: 'gemini-cli-mcp-client',
     version: '0.0.1',
   });
 
+  mcpClient.registerCapabilities({
+    roots: {},
+  });
+
+  mcpClient.setRequestHandler(ListRootsRequestSchema, async () => {
+    const roots = [];
+    for (const dir of workspaceContext.getDirectories()) {
+      roots.push({
+        uri: pathToFileURL(dir).toString(),
+        name: basename(dir),
+      });
+    }
+    return {
+      roots,
+    };
+  });
+
   // patch Client.callTool to use request timeout as genai McpCallTool.callTool does not do it
   // TODO: remove this hack once GenAI SDK does callTool with request options
   if ('callTool' in mcpClient) {