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API Builder

A workspace for REST API design

Design your API.
Before you build it.

Map your endpoints, connect your schemas, and get the structure right. A visual workspace for developers, from first idea to OpenAPI.

Start designing

No credit card required. Export your design when you need it.

Bookshop API

Example API Design

OpenAPI 3.0

Resource

Books

GET/books
POST/books
GET/books/{id}

Book

Schema
id
string
title
string
author
string

Auth scheme

Bearer JWT

ResponseResources, schemas, and auth. Connected.
One design. Two ways to work.Try the mode switch
Built around the standards you useOpenAPI 3.0JSON SchemaPostman

Clarity before code

The details belong together.

Not in scattered notes or separate files. Keep your endpoints, data shapes, and auth in one API Design.

01

See what connects.

Trace an endpoint to its response schema and auth requirements. Make those decisions before they become code.

GET /booksBook[]
02

Big picture. Small details.

Explore connections on the canvas. Switch to Flat Mode to focus on the details. The same design, either way.

CanvasFlat
03

Skip the blank canvas.

Describe what you want to build. Let the AI assistant create a starting point, then review and refine the design.

Your idea. A starting point.

Design with intention

Think it through. Then build it right.

Work out the shape of your API while changes are still design decisions, not code rewrites.

From idea to API Design

A clear path to your first export.

Start with a resource. Add the details. Take the result into the tools you already use.

01

Give your API a shape.

Create resources like Books or Orders. Add endpoints with methods, paths, and query parameters.

02

Make the contract explicit.

Define reusable request and response schemas. Connect auth schemes so each endpoint says what it needs.

03

Take it into your workflow.

Export OpenAPI as YAML or JSON, or download a Postman collection. Your design is not tied to the editor.

books.openapi.yamlOpenAPI 3.0
openapi: 3.0.3
info:
  title: Books API
  version: 1.0.0
paths:
  /books:
    get:
      summary: List books
      responses:
        '200':
          description: A list of books

Example excerpt · OpenAPI export

A few things to know

Before you start.

What API Builder does, what it does not, and where your design goes next.

What can I design here?

REST APIs with resources, endpoints, query parameters, reusable JSON Schemas, and auth schemes. Each API Design keeps these parts together in your workspace.

Does this build or host my backend?

No. API Builder is a design tool. It helps you define the API contract and export it. You implement and host the backend with your own tools.

Do I have to use the canvas?

No. Flat Mode lets you work through tabbed lists and a detail panel. You can switch between Canvas Mode and Flat Mode without creating a separate design.

Do I need AI to use it?

No. You can create and edit everything yourself. The AI assistant is an optional way to turn a description into a starting design. Review its output before using it.

What can I export?

An OpenAPI 3.0 document in YAML or JSON, or a Postman collection. Copy the generated output or download it from the editor.

Do I need an account?

Yes. Sign in to create and save API Designs in your personal workspace. No credit card is required. You can explore the example above without an account.

Start with the structure

Your next API starts here.

Turn the idea in your head into a design you can build from.

Start designing

No credit card required. Export your design when you need it.