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Workers AI now supports structured JSON outputs.

Feb 25, 2025, 03:00 PM

Workers AI

Workers AI now supports structured JSON outputs with JSON mode, which allows you to request a structured output response when interacting with AI models.

This makes it much easier to retrieve structured data from your AI models, and avoids the (error prone!) need to parse large unstructured text responses to extract your data.

JSON mode in Workers AI is compatible with the OpenAI SDK's structured outputs ↗ response_format API, which can be used directly in a Worker:

JavaScript

import { OpenAI } from "openai";

// Define your JSON schema for a calendar event
const CalendarEventSchema = {
  type: "object",
  properties: {
    name: { type: "string" },
    date: { type: "string" },
    participants: { type: "array", items: { type: "string" } },
  },
  required: ["name", "date", "participants"],
};

export default {
  async fetch(request, env) {
    const client = new OpenAI({
      apiKey: env.OPENAI_API_KEY,
      // Optional: use AI Gateway to bring logs, evals & caching to your AI requests
      // https://developers.cloudflare.com/ai-gateway/providers/openai/
      // baseUrl: "https://gateway.ai.cloudflare.com/v1/{account_id}/{gateway_id}/openai"
    });

    const response = await client.chat.completions.create({
      model: "gpt-4o-2024-08-06",
      messages: [
        { role: "system", content: "Extract the event information." },
        {
          role: "user",
          content: "Alice and Bob are going to a science fair on Friday.",
        },
      ],
      // Use the `response_format` option to request a structured JSON output
      response_format: {
        // Set json_schema and provide ra schema, or json_object and parse it yourself
        type: "json_schema",
        schema: CalendarEventSchema, // provide a schema
      },
    });

    // This will be of type CalendarEventSchema
    const event = response.choices[0].message.parsed;

    return Response.json({
      calendar_event: event,
    });
  },
};

TypeScript

import { OpenAI } from "openai";

interface Env {
  OPENAI_API_KEY: string;
}

// Define your JSON schema for a calendar event
const CalendarEventSchema = {
  type: 'object',
  properties: {
    name: { type: 'string' },
    date: { type: 'string' },
    participants: { type: 'array', items: { type: 'string' } },
  },
  required: ['name', 'date', 'participants']
};

export default {
  async fetch(request: Request, env: Env) {
    const client = new OpenAI({
      apiKey: env.OPENAI_API_KEY,
      // Optional: use AI Gateway to bring logs, evals & caching to your AI requests
      // https://developers.cloudflare.com/ai-gateway/providers/openai/
      // baseUrl: "https://gateway.ai.cloudflare.com/v1/{account_id}/{gateway_id}/openai"
    });

    const response = await client.chat.completions.create({
      model: 'gpt-4o-2024-08-06',
      messages: [
        { role: 'system', content: 'Extract the event information.' },
        { role: 'user', content: 'Alice and Bob are going to a science fair on Friday.' },
      ],
      // Use the `response_format` option to request a structured JSON output
      response_format: {
        // Set json_schema and provide ra schema, or json_object and parse it yourself
        type: 'json_schema',
        schema: CalendarEventSchema, // provide a schema
      },
    });

    // This will be of type CalendarEventSchema
    const event = response.choices[0].message.parsed;

    return Response.json({
      "calendar_event": event,
    })
  }
}

To learn more about JSON mode and structured outputs, visit the Workers AI documentation.