feat(plan): implement support for MCP servers in Plan mode (#18229)

packages/core/src/prompts/promptProvider.ts

@@ -26,6 +26,7 @@ import {
   ENTER_PLAN_MODE_TOOL_NAME,
 } from '../tools/tool-names.js';
 import { resolveModel, isPreviewModel } from '../config/models.js';
+import { DiscoveredMCPTool } from '../tools/mcp-tool.js';
 
 /**
  * Orchestrates prompt generation by gathering context and building options.
@@ -48,6 +49,7 @@ export class PromptProvider {
     const isPlanMode = approvalMode === ApprovalMode.PLAN;
     const skills = config.getSkillManager().getSkills();
     const toolNames = config.getToolRegistry().getAllToolNames();
+    const enabledToolNames = new Set(toolNames);
     const approvedPlanPath = config.getApprovedPlanPath();
 
     const desiredModel = resolveModel(
@@ -56,6 +58,28 @@ export class PromptProvider {
     );
     const isGemini3 = isPreviewModel(desiredModel);
 
+    // --- Context Gathering ---
+    let planModeToolsList = PLAN_MODE_TOOLS.filter((t) =>
+      enabledToolNames.has(t),
+    )
+      .map((t) => `- \`${t}\``)
+      .join('\n');
+
+    // Add read-only MCP tools to the list
+    if (isPlanMode) {
+      const allTools = config.getToolRegistry().getAllTools();
+      const readOnlyMcpTools = allTools.filter(
+        (t): t is DiscoveredMCPTool =>
+          t instanceof DiscoveredMCPTool && !!t.isReadOnly,
+      );
+      if (readOnlyMcpTools.length > 0) {
+        const mcpToolsList = readOnlyMcpTools
+          .map((t) => `- \`${t.name}\` (${t.serverName})`)
+          .join('\n');
+        planModeToolsList += `\n${mcpToolsList}`;
+      }
+    }
+
     let basePrompt: string;
 
     // --- Template File Override ---
@@ -105,11 +129,11 @@ export class PromptProvider {
           'primaryWorkflows',
           () => ({
             interactive: interactiveMode,
-            enableCodebaseInvestigator: toolNames.includes(
+            enableCodebaseInvestigator: enabledToolNames.has(
               CodebaseInvestigatorAgent.name,
             ),
-            enableWriteTodosTool: toolNames.includes(WRITE_TODOS_TOOL_NAME),
-            enableEnterPlanModeTool: toolNames.includes(
+            enableWriteTodosTool: enabledToolNames.has(WRITE_TODOS_TOOL_NAME),
+            enableEnterPlanModeTool: enabledToolNames.has(
               ENTER_PLAN_MODE_TOOL_NAME,
             ),
             approvedPlan: approvedPlanPath
@@ -121,11 +145,7 @@ export class PromptProvider {
         planningWorkflow: this.withSection(
           'planningWorkflow',
           () => ({
-            planModeToolsList: PLAN_MODE_TOOLS.filter((t) =>
-              new Set(toolNames).has(t),
-            )
-              .map((t) => `- \`${t}\``)
-              .join('\n'),
+            planModeToolsList,
             plansDir: config.storage.getProjectTempPlansDir(),
             approvedPlanPath: config.getApprovedPlanPath(),
           }),