Bedrock Action Groups: OpenAPI Tools That Typecheck Against Handlers

// tools/createBooking.ts
import { z } from "zod";

export const CreateBookingInput = z.object({
  idempotencyKey: z.string().uuid(),
  listingId: z.string().min(1),
  nights: z.number().int().min(1).max(30),
});
export type CreateBookingInput = z.infer<typeof CreateBookingInput>;

export async function handler(event: unknown) {
  const input = CreateBookingInput.parse(event); // ✅ runtime == schema
  return createBooking(input);
}

# ✅ Generate OpenAPI fragment for the action group
pnpm tsx scripts/zod-to-openapi.ts tools/*.ts > action-groups/bookings.openapi.json

// ci/assert-action-group-sync.ts
import { CreateBookingInput } from "../tools/createBooking";
import openapi from "../action-groups/bookings.openapi.json";

function schemasEqual(a: unknown, b: unknown) {
  return JSON.stringify(a) === JSON.stringify(b);
}

const fromZod = zodToJsonSchema(CreateBookingInput);
const fromOas = openapi.paths["/createBooking"].post.requestBody.content["application/json"].schema;

if (!schemasEqual(fromZod, fromOas)) {
  throw new Error("action_group_schema_drift"); // ✅ fail deploy
}

{
  "actionGroupName": "bookings",
  "apiSchema": { "payload": "<openapi>" },
  "actionGroupExecutor": { "lambda": "arn:aws:lambda:...:function:createBooking" },
  "functionSchema": null
}