fix: exclude access_mcp_resource tool when MCP has no resources (#9615)

src/core/prompts/__tests__/add-custom-instructions.spec.ts

@@ -170,7 +170,16 @@ const mockContext = {
 // Instead of extending McpHub, create a mock that implements just what we need
 const createMockMcpHub = (withServers: boolean = false): McpHub =>
 	({
-		getServers: () => (withServers ? [{ name: "test-server", disabled: false }] : []),
+		getServers: () =>
+			withServers
+				? [
+						{
+							name: "test-server",
+							disabled: false,
+							resources: [{ uri: "test://resource", name: "Test Resource" }],
+						},
+					]
+				: [],
 		getMcpServersPath: async () => "/mock/mcp/path",
 		getMcpSettingsFilePath: async () => "/mock/settings/path",
 		dispose: async () => {},

src/core/prompts/__tests__/system-prompt.spec.ts

@@ -173,7 +173,16 @@ const mockContext = {
 // Instead of extending McpHub, create a mock that implements just what we need
 const createMockMcpHub = (withServers: boolean = false): McpHub =>
 	({
-		getServers: () => (withServers ? [{ name: "test-server", disabled: false }] : []),
+		getServers: () =>
+			withServers
+				? [
+						{
+							name: "test-server",
+							disabled: false,
+							resources: [{ uri: "test://resource", name: "Test Resource" }],
+						},
+					]
+				: [],
 		getMcpServersPath: async () => "/mock/mcp/path",
 		getMcpSettingsFilePath: async () => "/mock/settings/path",
 		dispose: async () => {},

src/core/prompts/tools/__tests__/access-mcp-resource.spec.ts

@@ -0,0 +1,118 @@
+import { getAccessMcpResourceDescription } from "../access-mcp-resource"
+import { ToolArgs } from "../types"
+import { McpHub } from "../../../../services/mcp/McpHub"
+
+describe("getAccessMcpResourceDescription", () => {
+	const baseArgs: Omit<ToolArgs, "mcpHub"> = {
+		cwd: "/test",
+		supportsComputerUse: false,
+	}
+
+	it("should return undefined when mcpHub is not provided", () => {
+		const args: ToolArgs = {
+			...baseArgs,
+			mcpHub: undefined,
+		}
+
+		const result = getAccessMcpResourceDescription(args)
+		expect(result).toBeUndefined()
+	})
+
+	it("should return undefined when mcpHub has no servers with resources", () => {
+		const mockMcpHub = {
+			getServers: () => [
+				{
+					name: "test-server",
+					resources: [],
+				},
+			],
+		} as unknown as McpHub
+
+		const args: ToolArgs = {
+			...baseArgs,
+			mcpHub: mockMcpHub,
+		}
+
+		const result = getAccessMcpResourceDescription(args)
+		expect(result).toBeUndefined()
+	})
+
+	it("should return undefined when mcpHub has servers with undefined resources", () => {
+		const mockMcpHub = {
+			getServers: () => [
+				{
+					name: "test-server",
+					resources: undefined,
+				},
+			],
+		} as unknown as McpHub
+
+		const args: ToolArgs = {
+			...baseArgs,
+			mcpHub: mockMcpHub,
+		}
+
+		const result = getAccessMcpResourceDescription(args)
+		expect(result).toBeUndefined()
+	})
+
+	it("should return undefined when mcpHub has no servers", () => {
+		const mockMcpHub = {
+			getServers: () => [],
+		} as unknown as McpHub
+
+		const args: ToolArgs = {
+			...baseArgs,
+			mcpHub: mockMcpHub,
+		}
+
+		const result = getAccessMcpResourceDescription(args)
+		expect(result).toBeUndefined()
+	})
+
+	it("should return description when mcpHub has servers with resources", () => {
+		const mockMcpHub = {
+			getServers: () => [
+				{
+					name: "test-server",
+					resources: [{ uri: "test://resource", name: "Test Resource" }],
+				},
+			],
+		} as unknown as McpHub
+
+		const args: ToolArgs = {
+			...baseArgs,
+			mcpHub: mockMcpHub,
+		}
+
+		const result = getAccessMcpResourceDescription(args)
+		expect(result).toBeDefined()
+		expect(result).toContain("## access_mcp_resource")
+		expect(result).toContain("server_name")
+		expect(result).toContain("uri")
+	})
+
+	it("should return description when at least one server has resources", () => {
+		const mockMcpHub = {
+			getServers: () => [
+				{
+					name: "server-without-resources",
+					resources: [],
+				},
+				{
+					name: "server-with-resources",
+					resources: [{ uri: "test://resource", name: "Test Resource" }],
+				},
+			],
+		} as unknown as McpHub
+
+		const args: ToolArgs = {
+			...baseArgs,
+			mcpHub: mockMcpHub,
+		}
+
+		const result = getAccessMcpResourceDescription(args)
+		expect(result).toBeDefined()
+		expect(result).toContain("## access_mcp_resource")
+	})
+})

src/core/prompts/tools/__tests__/filter-tools-for-mode.spec.ts

@@ -71,7 +71,15 @@ describe("filterNativeToolsForMode", () => {
 			groups: ["read", "browser", "mcp"] as const,
 		}
 
-		const filtered = filterNativeToolsForMode(mockNativeTools, "architect", [architectMode], {}, undefined, {})
+		const filtered = filterNativeToolsForMode(
+			mockNativeTools,
+			"architect",
+			[architectMode],
+			{},
+			undefined,
+			{},
+			undefined,
+		)
 
 		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
 
@@ -101,7 +109,7 @@ describe("filterNativeToolsForMode", () => {
 			groups: ["read", "edit", "browser", "command", "mcp"] as const,
 		}
 
-		const filtered = filterNativeToolsForMode(mockNativeTools, "code", [codeMode], {}, undefined, {})
+		const filtered = filterNativeToolsForMode(mockNativeTools, "code", [codeMode], {}, undefined, {}, undefined)
 
 		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
 
@@ -123,7 +131,15 @@ describe("filterNativeToolsForMode", () => {
 			groups: [] as const, // No groups
 		}
 
-		const filtered = filterNativeToolsForMode(mockNativeTools, "restrictive", [restrictiveMode], {}, undefined, {})
+		const filtered = filterNativeToolsForMode(
+			mockNativeTools,
+			"restrictive",
+			[restrictiveMode],
+			{},
+			undefined,
+			{},
+			undefined,
+		)
 
 		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
 
@@ -138,7 +154,7 @@ describe("filterNativeToolsForMode", () => {
 	})
 
 	it("should handle undefined mode by using default mode", () => {
-		const filtered = filterNativeToolsForMode(mockNativeTools, undefined, undefined, {}, undefined, {})
+		const filtered = filterNativeToolsForMode(mockNativeTools, undefined, undefined, {}, undefined, {}, undefined)
 
 		// Should return some tools (default mode is code which has all groups)
 		expect(filtered.length).toBeGreaterThan(0)
@@ -168,11 +184,136 @@ describe("filterNativeToolsForMode", () => {
 		const toolsWithCodebaseSearch = [...mockNativeTools, mockCodebaseSearchTool]
 
 		// Without codeIndexManager
-		const filtered = filterNativeToolsForMode(toolsWithCodebaseSearch, "code", [codeMode], {}, undefined, {})
+		const filtered = filterNativeToolsForMode(
+			toolsWithCodebaseSearch,
+			"code",
+			[codeMode],
+			{},
+			undefined,
+			{},
+			undefined,
+		)
 		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
 		expect(toolNames).not.toContain("codebase_search")
 	})
 
+	it("should exclude access_mcp_resource when mcpHub is not provided", () => {
+		const codeMode: ModeConfig = {
+			slug: "code",
+			name: "Code",
+			roleDefinition: "Test",
+			groups: ["read", "edit", "browser", "command", "mcp"] as const,
+		}
+
+		const mockAccessMcpResourceTool: OpenAI.Chat.ChatCompletionTool = {
+			type: "function",
+			function: {
+				name: "access_mcp_resource",
+				description: "Access MCP resource",
+				parameters: {},
+			},
+		}
+
+		const toolsWithAccessMcpResource = [...mockNativeTools, mockAccessMcpResourceTool]
+
+		// Without mcpHub
+		const filtered = filterNativeToolsForMode(
+			toolsWithAccessMcpResource,
+			"code",
+			[codeMode],
+			{},
+			undefined,
+			{},
+			undefined,
+		)
+		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
+		expect(toolNames).not.toContain("access_mcp_resource")
+	})
+
+	it("should exclude access_mcp_resource when mcpHub has no resources", () => {
+		const codeMode: ModeConfig = {
+			slug: "code",
+			name: "Code",
+			roleDefinition: "Test",
+			groups: ["read", "edit", "browser", "command", "mcp"] as const,
+		}
+
+		const mockAccessMcpResourceTool: OpenAI.Chat.ChatCompletionTool = {
+			type: "function",
+			function: {
+				name: "access_mcp_resource",
+				description: "Access MCP resource",
+				parameters: {},
+			},
+		}
+
+		const toolsWithAccessMcpResource = [...mockNativeTools, mockAccessMcpResourceTool]
+
+		// Mock mcpHub with no resources
+		const mockMcpHub = {
+			getServers: () => [
+				{
+					name: "test-server",
+					resources: [],
+				},
+			],
+		} as any
+
+		const filtered = filterNativeToolsForMode(
+			toolsWithAccessMcpResource,
+			"code",
+			[codeMode],
+			{},
+			undefined,
+			{},
+			mockMcpHub,
+		)
+		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
+		expect(toolNames).not.toContain("access_mcp_resource")
+	})
+
+	it("should include access_mcp_resource when mcpHub has resources", () => {
+		const codeMode: ModeConfig = {
+			slug: "code",
+			name: "Code",
+			roleDefinition: "Test",
+			groups: ["read", "edit", "browser", "command", "mcp"] as const,
+		}
+
+		const mockAccessMcpResourceTool: OpenAI.Chat.ChatCompletionTool = {
+			type: "function",
+			function: {
+				name: "access_mcp_resource",
+				description: "Access MCP resource",
+				parameters: {},
+			},
+		}
+
+		const toolsWithAccessMcpResource = [...mockNativeTools, mockAccessMcpResourceTool]
+
+		// Mock mcpHub with resources
+		const mockMcpHub = {
+			getServers: () => [
+				{
+					name: "test-server",
+					resources: [{ uri: "test://resource", name: "Test Resource" }],
+				},
+			],
+		} as any
+
+		const filtered = filterNativeToolsForMode(
+			toolsWithAccessMcpResource,
+			"code",
+			[codeMode],
+			{},
+			undefined,
+			{},
+			mockMcpHub,
+		)
+		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
+		expect(toolNames).toContain("access_mcp_resource")
+	})
+
 	it("should exclude update_todo_list when todoListEnabled is false", () => {
 		const codeMode: ModeConfig = {
 			slug: "code",
@@ -192,9 +333,17 @@ describe("filterNativeToolsForMode", () => {
 
 		const toolsWithTodo = [...mockNativeTools, mockTodoTool]
 
-		const filtered = filterNativeToolsForMode(toolsWithTodo, "code", [codeMode], {}, undefined, {
-			todoListEnabled: false,
-		})
+		const filtered = filterNativeToolsForMode(
+			toolsWithTodo,
+			"code",
+			[codeMode],
+			{},
+			undefined,
+			{
+				todoListEnabled: false,
+			},
+			undefined,
+		)
 		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
 		expect(toolNames).not.toContain("update_todo_list")
 	})
@@ -225,6 +374,7 @@ describe("filterNativeToolsForMode", () => {
 			{ imageGeneration: false },
 			undefined,
 			{},
+			undefined,
 		)
 		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
 		expect(toolNames).not.toContain("generate_image")
@@ -256,6 +406,7 @@ describe("filterNativeToolsForMode", () => {
 			{ runSlashCommand: false },
 			undefined,
 			{},
+			undefined,
 		)
 		const toolNames = filtered.map((t) => ("function" in t ? t.function.name : ""))
 		expect(toolNames).not.toContain("run_slash_command")

src/core/prompts/tools/access-mcp-resource.ts

@@ -1,7 +1,16 @@
 import { ToolArgs } from "./types"
+import { McpHub } from "../../../services/mcp/McpHub"
+
+/**
+ * Helper function to check if any MCP server has resources available
+ */
+function hasAnyMcpResources(mcpHub: McpHub): boolean {
+	const servers = mcpHub.getServers()
+	return servers.some((server) => server.resources && server.resources.length > 0)
+}
 
 export function getAccessMcpResourceDescription(args: ToolArgs): string | undefined {
-	if (!args.mcpHub) {
+	if (!args.mcpHub || !hasAnyMcpResources(args.mcpHub)) {
 		return undefined
 	}
 	return `## access_mcp_resource

src/core/prompts/tools/filter-tools-for-mode.ts

@@ -4,6 +4,7 @@ import { getModeBySlug, getToolsForMode, isToolAllowedForMode } from "../../../s
 import { TOOL_GROUPS, ALWAYS_AVAILABLE_TOOLS } from "../../../shared/tools"
 import { defaultModeSlug } from "../../../shared/modes"
 import type { CodeIndexManager } from "../../../services/code-index/manager"
+import type { McpHub } from "../../../services/mcp/McpHub"
 
 /**
  * Filters native tools based on mode restrictions.
@@ -15,6 +16,7 @@ import type { CodeIndexManager } from "../../../services/code-index/manager"
  * @param experiments - Experiment flags
  * @param codeIndexManager - Code index manager for codebase_search feature check
  * @param settings - Additional settings for tool filtering
+ * @param mcpHub - MCP hub for checking available resources
  * @returns Filtered array of tools allowed for the mode
  */
 export function filterNativeToolsForMode(
@@ -24,6 +26,7 @@ export function filterNativeToolsForMode(
 	experiments: Record<string, boolean> | undefined,
 	codeIndexManager?: CodeIndexManager,
 	settings?: Record<string, any>,
+	mcpHub?: McpHub,
 ): OpenAI.Chat.ChatCompletionTool[] {
 	// Get mode configuration and all tools for this mode
 	const modeSlug = mode ?? defaultModeSlug
@@ -81,6 +84,11 @@ export function filterNativeToolsForMode(
 		allowedToolNames.delete("browser_action")
 	}
 
+	// Conditionally exclude access_mcp_resource if MCP is not enabled or there are no resources
+	if (!mcpHub || !hasAnyMcpResources(mcpHub)) {
+		allowedToolNames.delete("access_mcp_resource")
+	}
+
 	// Filter native tools based on allowed tool names
 	return nativeTools.filter((tool) => {
 		// Handle both ChatCompletionTool and ChatCompletionCustomTool
@@ -91,6 +99,14 @@ export function filterNativeToolsForMode(
 	})
 }
 
+/**
+ * Helper function to check if any MCP server has resources available
+ */
+function hasAnyMcpResources(mcpHub: McpHub): boolean {
+	const servers = mcpHub.getServers()
+	return servers.some((server) => server.resources && server.resources.length > 0)
+}
+
 /**
  * Checks if a specific tool is allowed in the current mode.
  * This is useful for dynamically filtering system prompt content.

src/core/task/build-tools.ts

@@ -52,6 +52,7 @@ export async function buildNativeToolsArray(options: BuildToolsOptions): Promise
 		experiments,
 		codeIndexManager,
 		filterSettings,
+		mcpHub,
 	)
 
 	// Filter MCP tools based on mode restrictions