SDL stands for Schema Definition Language, the human-readable syntax GraphQL uses to declare types, fields, queries, and mutations. Servers like Apollo and graphql-js parse SDL into an executable schema.

What does the exclamation mark mean?

A trailing exclamation mark marks a field as non-null, meaning the API guarantees a value. Without it the field is nullable and may return null in a response.

What are input types for?

Mutations cannot take object types as arguments, so GraphQL uses input types to bundle arguments. The builder emits a matching input type per entity for create and update operations.

Do I get an ID field automatically?

Yes. Each generated object type includes an id field of type ID, which is the conventional non-null primary key GraphQL clients expect for caching and refetching.

How do I use the generated mutations?

Each entity gets create, update, and delete mutations referencing its input type. You still write resolvers, but the signatures and argument shapes are defined for you so the contract is fixed.

GraphQL Schema Builder

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Generate a GraphQL schema fast

A GraphQL schema is the contract between client and server. Writing the SDL by hand means repeating the same type, input, Query, and Mutation boilerplate for every entity. This builder takes a compact list of entities and fields and produces a complete, valid schema you can drop straight into your server’s typeDefs.

How it works

Each entity block becomes an object type with the fields you list plus a non-null id: ID!. Fields are parsed as name: Type, where a trailing ! keeps the non-null marker and [Type] denotes a list. When input types are enabled, every entity also gets a matching input type with the same fields minus id, since clients supply ids only for updates. The Query type gains a singular field that takes an id and a plural list field per entity. With mutations enabled, each entity gets create, update, and delete fields whose arguments reference the generated input type, following the standard CRUD convention.

Tips and example

Write one entity per block, for example a User type with name: String! and email: String!, then a Post type with title: String! and author: User. Reference other entity names directly to build relationships. Use [Post!]! for a non-null list of non-null posts. After generating, paste the SDL into Apollo Server’s typeDefs and write resolvers matching the field names.