feat: add MCP servers to agent mode

- Update agent mode to use prepareMcpConfig instead of empty config
- Update prepareMcpConfig to accept both ParsedGitHubContext and AutomationContext
- Add type guards for context-specific properties (isPR, entityNumber)
- This enables bot actors to use full MCP capabilities via workflow_dispatch

src/mcp/install-mcp-server.ts

@@ -1,6 +1,6 @@
 import * as core from "@actions/core";
 import { GITHUB_API_URL, GITHUB_SERVER_URL } from "../github/api/config";
-import type { ParsedGitHubContext } from "../github/context";
+import type { GitHubContext } from "../github/context";
 import { Octokit } from "@octokit/rest";
 
 type PrepareConfigParams = {
@@ -12,7 +12,7 @@ type PrepareConfigParams = {
   additionalMcpConfig?: string;
   claudeCommentId?: string;
   allowedTools: string[];
-  context: ParsedGitHubContext;
+  context: GitHubContext;
 };
 
 async function checkActionsReadPermission(
@@ -115,7 +115,7 @@ export async function prepareMcpConfig(
     const hasActionsReadPermission =
       context.inputs.additionalPermissions.get("actions") === "read";
 
-    if (context.isPR && hasActionsReadPermission) {
+    if ('isPR' in context && context.isPR && hasActionsReadPermission) {
       // Verify the token actually has actions:read permission
       const actuallyHasPermission = await checkActionsReadPermission(
         process.env.ACTIONS_TOKEN || "",
@@ -141,7 +141,7 @@ export async function prepareMcpConfig(
           GITHUB_TOKEN: process.env.ACTIONS_TOKEN,
           REPO_OWNER: owner,
           REPO_NAME: repo,
-          PR_NUMBER: context.entityNumber?.toString() || "",
+          PR_NUMBER: 'entityNumber' in context ? context.entityNumber?.toString() || "" : "",
           RUNNER_TEMP: process.env.RUNNER_TEMP || "/tmp",
         },
       };

src/modes/agent/index.ts

@@ -1,7 +1,8 @@
 import * as core from "@actions/core";
-import { mkdir, writeFile } from "fs/promises";
 import type { Mode, ModeOptions, ModeResult } from "../types";
 import { isAutomationContext } from "../../github/context";
+import type { PreparedContext } from "../../create-prompt/types";
+import { prepareMcpConfig } from "../../mcp/install-mcp-server";
 
 /**
  * Agent mode implementation.
@@ -39,27 +40,10 @@ export const agentMode: Mode = {
     return false;
   },
 
-  async prepare({ context }: ModeOptions): Promise<ModeResult> {
+  async prepare({ context, githubToken }: ModeOptions): Promise<ModeResult> {
     // Agent mode handles automation events (workflow_dispatch, schedule) only
 
-    // Create prompt directory
-    await mkdir(`${process.env.RUNNER_TEMP}/claude-prompts`, {
-      recursive: true,
-    });
-
-    // Write the prompt file - the base action requires a prompt_file parameter,
-    // so we must create this file even though agent mode typically uses
-    // override_prompt or direct_prompt. If neither is provided, we write
-    // a minimal prompt with just the repository information.
-    const promptContent =
-      context.inputs.overridePrompt ||
-      context.inputs.directPrompt ||
-      `Repository: ${context.repository.owner}/${context.repository.repo}`;
-
-    await writeFile(
-      `${process.env.RUNNER_TEMP}/claude-prompts/claude-prompt.txt`,
-      promptContent,
-    );
+    // Agent mode doesn't need to create prompt files here - handled by createPrompt
 
     // Export tool environment variables for agent mode
     const baseTools = [
@@ -80,29 +64,25 @@ export const agentMode: Mode = {
       ...context.inputs.disallowedTools,
     ];
 
-    core.exportVariable("ALLOWED_TOOLS", allowedTools.join(","));
-    core.exportVariable("DISALLOWED_TOOLS", disallowedTools.join(","));
+    // Export as INPUT_ prefixed variables for the base action
+    core.exportVariable("INPUT_ALLOWED_TOOLS", allowedTools.join(","));
+    core.exportVariable("INPUT_DISALLOWED_TOOLS", disallowedTools.join(","));
 
-    // Agent mode uses a minimal MCP configuration
-    // We don't need comment servers or PR-specific tools for automation
-    const mcpConfig: any = {
-      mcpServers: {},
-    };
-
-    // Add user-provided additional MCP config if any
+    // Get MCP configuration using the same setup as other modes
     const additionalMcpConfig = process.env.MCP_CONFIG || "";
-    if (additionalMcpConfig.trim()) {
-      try {
-        const additional = JSON.parse(additionalMcpConfig);
-        if (additional && typeof additional === "object") {
-          Object.assign(mcpConfig, additional);
-        }
-      } catch (error) {
-        core.warning(`Failed to parse additional MCP config: ${error}`);
-      }
-    }
+    const mcpConfig = await prepareMcpConfig({
+      githubToken,
+      owner: context.repository.owner,
+      repo: context.repository.repo,
+      branch: "", // Agent mode doesn't use branches
+      baseBranch: "",
+      additionalMcpConfig,
+      claudeCommentId: undefined, // Agent mode doesn't track comments
+      allowedTools: [...baseTools, ...context.inputs.allowedTools],
+      context,
+    });
 
-    core.setOutput("mcp_config", JSON.stringify(mcpConfig));
+    core.setOutput("mcp_config", mcpConfig);
 
     return {
       commentId: undefined,
@@ -111,7 +91,21 @@ export const agentMode: Mode = {
         currentBranch: "",
         claudeBranch: undefined,
       },
-      mcpConfig: JSON.stringify(mcpConfig),
+      mcpConfig: mcpConfig,
     };
   },
+
+  generatePrompt(context: PreparedContext): string {
+    // Agent mode uses override or direct prompt, no GitHub data needed
+    if (context.overridePrompt) {
+      return context.overridePrompt;
+    }
+
+    if (context.directPrompt) {
+      return context.directPrompt;
+    }
+
+    // Minimal fallback - repository is a string in PreparedContext
+    return `Repository: ${context.repository}`;
+  },
 };