nextjs_index

Discover all running Next.js development servers and list their available MCP tools. WHEN TO USE THIS TOOL - Use proactively in these scenarios: 1. Before implementing ANY changes to the app: When asked to add, modify, or fix anything in the application: - "Add a loading state" → Check current component structure and routes first - "Fix the navigation" → Inspect existing routes and components - "Update the API endpoint" → Query current routes and data flows - "Add error handling" → Check runtime errors and component hierarchy - "Refactor the auth logic" → Inspect current auth implementation and routes - "Optimize performance" → Check runtime diagnostics and component tree Use this to understand where changes should be made and what currently exists. 2. For diagnostic and investigation questions: - "What's happening?" / "What's going on?" / "Why isn't this working?" - "Check the errors" / "See what's wrong" - "What routes are available?" / "Show me the routes" - "Clear the cache" / "Reset everything" - Questions about build status, compilation errors, or runtime diagnostics 3. For agentic codebase search: Use this as FIRST CHOICE for searching the currently running app. If not found, fallback to static codebase search tools. KEY PRINCIPLE: If the request involves the running Next.js application (whether to investigate OR modify it), query the runtime FIRST to understand current state before proceeding. REQUIREMENTS: - Next.js 16 or later (MCP support was added in v16) - If you're on Next.js 15 or earlier, upgrade first by running 'npx @next/codemod@latest upgrade latest' Next.js 16+ exposes an MCP (Model Context Protocol) endpoint at /_next/mcp automatically when the dev server starts. No configuration needed - MCP is enabled by default in Next.js 16 and later. This tool discovers all running Next.js servers and returns: - Server port, PID, and URL - Complete list of available MCP tools for each server - Tool descriptions and input schemas After calling this tool, use 'nextjs_call' to execute specific tools. [IMPORTANT] If auto-discovery returns no servers: 1. Ask the user which port their Next.js dev server is running on 2. Call this tool again with the 'port' parameter set to the user-provided port If the MCP endpoint is not available: 1. Ensure you're running Next.js 16 or later (upgrade with 'npx @next/codemod@latest upgrade latest') 2. Verify the dev server is running (npm run dev) 3. Check that the dev server started successfully without errors. It is categorised as a Read tool in the Next Devtools MCP Server, which means it retrieves data without modifying state.

nextjs_index accepts 1 parameter: port. The full parameter table on this page comes from the server's own tool schema.

Register the Next Devtools MCP server in PolicyLayer and add a rule for nextjs_index: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Next Devtools. Nothing to install.

nextjs_index is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Yes. Add a rate_limit block to the nextjs_index rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

Set action: deny in the PolicyLayer policy for nextjs_index. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

nextjs_index is provided by the Next Devtools MCP server (next-devtools-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.