integration · Next.js

Next.js MCP integration.

Your Next.js 15 app already has API routes; here's how to expose them as MCP tools without rewriting a single handler. Publish an OpenAPI spec, point wmcp.sh at it, and any MCP-compatible agent (Claude Desktop, Cursor, Codex) gets typed tools.

wmcp.sh is not affiliated with Vercel or Anthropic. App Router and Route Handlers are Next.js features.

The gap

You have the API. You don't have the MCP server.

What you have today

Route Handlers under app/api/**/route.ts serving your web app, with typed inputs (Zod, valibot, or hand-rolled), Vercel deployment, and probably some Zod-to-OpenAPI generator emitting a spec.

What agents need

A Model Context Protocol server exposing each route as a tool with JSON Schema inputs and structured outputs. wmcp.sh generates it from your existing OpenAPI doc — no new handler, no new framework.

The wiring

One Route Handler, exposed as a tool.

A real, runnable example. The handler is plain Next.js 15; the OpenAPI bit is what wmcp.sh ingests.

// app/api/quotes/route.ts — Next.js 15 App Router
import { NextResponse } from 'next/server';
import { z } from 'zod';

export const runtime = 'edge';

const QuoteInput = z.object({
  symbol: z.string().min(1).max(12),
  size: z.number().positive(),
});

export async function POST(req: Request) {
  const body = QuoteInput.parse(await req.json());
  const mid = await fetchMid(body.symbol);
  return NextResponse.json({
    symbol: body.symbol,
    bid: mid * 0.999,
    ask: mid * 1.001,
    size: body.size,
    issued_at: new Date().toISOString(),
  });
}

// Publish OpenAPI at /api/openapi (next-rest-framework, zod-to-openapi, or hand-rolled).
// Then point wmcp.sh at https://acme.example.com/api/openapi and every route
// becomes an MCP tool the agent can call.

Once the spec is live, register it once: curl 'https://wmcp.sh/api/v1/tools?url=https://acme.example.com/api/openapi'. See /integration/openapi for the full spec-ingest contract.

Side-by-side

Hand-rolled MCP server vs wmcp.sh ingest.

CapabilityHand-rolled MCP serverwmcp.sh + Next.js OpenAPI
Tool schema generation ⚠️ You write a tools.ts and keep it in sync with Route Handlers ✅ Auto-generated from the OpenAPI spec your build already emits
Streamable HTTP transport ⚠️ You implement the MCP spec server yourself ✅ Served at https://wmcp.sh/mcp/<your-id> with SSE + HTTP fallback
Authentication forwarding ⚠️ Custom middleware in every Route Handler ✅ Bearer / OAuth 2.1 / API-key passthrough configured per spec
Edge Runtime support ✅ Yes, if you keep the MCP server edge-compatible ✅ wmcp.sh runs on Cloudflare Workers; your origin can be Edge or Node
Per-tool rate limit ⚠️ Manual ✅ Token-bucket per MCP client at the proxy edge
Spec drift detection ❌ Silent breakage when handler diverges from tools.ts ✅ Spec is the source of truth; re-ingest on deploy
FAQ

Common questions from Next.js teams.

Do I need to rewrite my Route Handlers?
No. Your app/api/**/route.ts files stay as-is. wmcp.sh consumes an OpenAPI document describing them and generates MCP tool definitions. Most teams generate the spec with a Zod-to-OpenAPI library or hand-write a small static file.
Does this work with Edge Runtime and Vercel?
Yes. The wmcp.sh proxy doesn't care whether your origin runs on the Vercel Edge Runtime, Node, or a static export with a separate backend. If the URL responds, MCP clients can call it.
How does authentication work?
Three patterns: pass-through bearer (wmcp.sh forwards Authorization), OAuth 2.1 proxy at /mcp/<provider> for DCR-compliant origins, or per-tool API keys declared in your spec's securitySchemes.
What about Server Actions?
Server Actions are RPC over POST without a stable public URL or schema. For MCP exposure, wrap the same logic in a Route Handler with a typed input. The handler can be one line that calls the action.
Can I gate which routes become tools?
Yes — tag operations in your OpenAPI spec and pass &tag=public to the ingest URL. Untagged or excluded operations stay invisible to MCP clients.
What versions of Next.js are supported?
Next 13.4+ App Router works the same way (Route Handlers shipped GA in 13.4). The example targets Next 15 because that's current. Pages Router API routes work too if you can publish an OpenAPI spec for them.
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