prompt-as-endpoint

Helper library for creating HTTP endpoints that use LLMs to return schema-validated JSON responses.

Installation

npm install prompt-as-endpoint

Usage

import { createEndpointHandler } from 'prompt-as-endpoint';
import { z } from 'zod';

const handler = createEndpointHandler({
  inputSchema: z.object({ name: z.string(), style: z.string() }),
  outputSchema: z.object({ greeting: z.string(), mood: z.string() }),
  prompt: 'Greet {name} in a {style} way. Respond with JSON only.',
  call: async (messages) => {
    // call your LLM here, return the response string
  },
});

// handler(input) returns a typed, validated result — wire it into your framework directly:

Framework integration

The handler is a plain async function. Wire it into your framework with a few lines:

Hono

app.post('/greet', async (c) => {
  const parsed = handler.inputSchema.safeParse(await c.req.json());
  if (!parsed.success) return c.json({ error: parsed.error.flatten() }, 400);
  return c.json(await handler(parsed.data));
});

Express

app.post('/greet', async (req, res) => {
  const parsed = handler.inputSchema.safeParse(req.body);
  if (!parsed.success) return res.status(400).json({ error: parsed.error.flatten() });
  res.json(await handler(parsed.data));
});

Next.js App Router

export async function POST(request: NextRequest) {
  const parsed = handler.inputSchema.safeParse(await request.json());
  if (!parsed.success) return NextResponse.json({ error: parsed.error.flatten() }, { status: 400 });
  return NextResponse.json(await handler(parsed.data));
}

License

MIT