How is this different from the GraphQL Query Tester?

The GraphQL Query Tester runs a query against a live endpoint. This tool generates a brand-new schema (SDL) from a described data model, for when you're designing a schema before an endpoint or resolver implementation exists.

What does the required toggle actually do?

It adds GraphQL's non-null marker ("!") after the field's type, e.g. String! instead of String. A required field can never resolve to null without the GraphQL server itself raising an error, so only mark a field required if your data genuinely always has a value for it.

What does the list toggle produce?

It wraps the scalar type in brackets with a non-null list-item marker, e.g. [String!] for a list of strings, following GraphQL's convention that list items themselves are typically marked non-null even when the list field is nullable.

Why does every mutation assume an "id" argument for update and delete?

The generated update and delete mutations always take an id: ID! argument regardless of whether you defined an explicit "id" field, following the common GraphQL convention that every persisted object is looked up and mutated by an ID. Adjust the generated stub if your data model doesn't use that convention.

GraphQL Schema Generator - SDL from a Data Model

Overview

Introduction

Sketching a GraphQL schema by hand means writing the type definitions, then separately remembering to add matching Query fields and the create/update/delete mutation trio for each type, an easy step to forget or get inconsistent between types.

This tool generates all three from one described data model, entirely in your browser.

What Is GraphQL Schema Generator?

A GraphQL SDL generator that takes repeatable type rows (a type name plus named, scalar-typed fields) and produces type definitions, a Query type, and a Mutation type with create/update/delete stubs.

It's part of this site's API Tools collection, and complements the existing GraphQL Query Tester (which runs queries against a live endpoint) and GraphQL to REST Mapping Helper (which maps an existing schema to REST) rather than replacing either.

How GraphQL Schema Generator Works

Each type row's fields are validated as legal GraphQL names and rendered as `name: Type` lines inside a `type TypeName { ... }` block, with required and list toggles adding GraphQL's `!` non-null marker and `[...]` list brackets respectively.

For every type, a singular lookup-by-ID field and a plural list field are added to the generated Query type, and create/update/delete mutation stubs are added to the generated Mutation type, with create taking all of the type's fields as arguments, update taking an id plus each field made nullable, and delete taking only an id and returning a Boolean.

When To Use GraphQL Schema Generator

Use it when sketching out a new GraphQL API's data model and you want a starting schema with the conventional query/mutation shape already wired up.

It's also useful for quickly producing a consistent set of CRUD-style operations across several types, rather than hand-writing the same Query/Mutation pattern repeatedly.

Often used alongside OpenAPI Generator and Postman Collection Generator.

Features

Advantages

Generates the type definitions, Query fields, and Mutation stubs together in one pass, so they stay consistent across every type in the model.
Validates every type and field name against GraphQL's naming rules before generating anything.
Applies pluralization for the list query field name (category → categories, tag → tags) rather than a naive plural-s suffix.

Limitations

Only scalar field types (ID, String, Int, Float, Boolean) are supported; object references between your own types (like a Post type with an author: User field) aren't modeled.
Generated mutations are structural stubs only; there's no resolver logic, and update/delete always assume an id-based lookup convention.
Doesn't generate interfaces, unions, enums, or input types, only object types, Query, and Mutation.

Examples

A single Product type

Input

types: [{typeName: "Product", fields: [{name: "id", scalarType: ID, required: true, isList: false}, {name: "name", scalarType: String, required: true, isList: false}, {name: "tags", scalarType: String, required: false, isList: true}]}]

Output

type Product {
  id: ID!
  name: String!
  tags: [String!]
}

type Query {
  product(id: ID!): Product
  products: [Product!]!
}

type Mutation {
  createProduct(id: ID!, name: String!, tags: [String!]): Product!
  updateProduct(id: ID!, name: String, tags: [String!]): Product
  deleteProduct(id: ID!): Boolean!
}

Product gets a singular product(id) query and a plural products list query, plus create/update/delete mutations built from its three fields; updateProduct's own id field is folded into the leading id: ID! argument rather than duplicated.

Best Practices & Notes

Best Practices

Mark a field required only when your underlying data source genuinely never returns null for it; an incorrectly required field causes real runtime errors once resolvers are wired up.
Review the generated update mutation's arguments and remove any that shouldn't be independently editable (like a createdAt timestamp) before implementing its resolver.
Add object-reference fields between your types by hand afterward; this generator intentionally keeps to scalar fields to keep the described model simple to fill in.

Developer Notes

Pluralization for the list query field name uses a small heuristic (consonant + y → ies, s/x/z/ch/sh → es, otherwise + s) rather than a full pluralization library, which covers the overwhelming majority of common English type names without adding a dependency; the update mutation always prepends its own `id: ID!` argument ahead of the type's other fields (rendered as nullable, list-aware types without the required `!`), and if the described type already has its own field named "id" that field is excluded from the rest of the argument list so it isn't declared twice.

GraphQL Schema Generator Use Cases

Scaffolding a first-draft GraphQL schema for a new API, including the conventional Query/Mutation shape
Producing a consistent CRUD-style operation set across several types in a data model
Teaching or demonstrating GraphQL SDL conventions (non-null, lists, Query/Mutation structure) with a concrete generated example

Common Mistakes

Treating the generated mutations as resolver-complete; they're SDL stubs describing the operation's shape, not implementations.
Marking every field required by default, which produces a schema that can't gracefully represent missing or not-yet-available data.

Tips

If two types reference each other (like Post and Author), generate this schema first for the scalar fields, then hand-add the object-reference fields connecting the types.

GraphQL Schema Generator