GraphQL Schema Linter

It validates SDL syntax structure and checks for: missing Query type, fields without descriptions, deprecated fields and types, naming convention violations (types PascalCase, fields camelCase, enum values SCREAMING_SNAKE_CASE), ID field type consistency, missing pagination on list fields, and custom scalar declarations.

SDL stands for Schema Definition Language. It is the official way to define a GraphQL schema in a human-readable text format. You define types with type TypeName { fieldName: FieldType }, input types, enums, interfaces, unions, and the root Query/Mutation/Subscription types. SDL is used in schema-first development and by tools like Apollo Studio, GraphQL Inspector, and graphql-codegen.

Descriptions appear in GraphQL Playground, Apollo Studio, and any introspection-based documentation tool. Without descriptions, API consumers have no context for what a field means, what values are valid, or what side effects it has. Descriptions are added with triple quotes: """User's email address, used for login.""" before the field.

The @deprecated directive marks a field, argument, or enum value as deprecated. It takes an optional reason parameter: fieldName: String @deprecated(reason: "Use newField instead"). Introspection and GraphQL clients can detect deprecated fields and show warnings to developers. This is the correct way to sunset API fields without breaking clients.

Types: PascalCase (User, CreateUserInput, UserRole). Fields and arguments: camelCase (firstName, createdAt, userId). Enum values: SCREAMING_SNAKE_CASE (ACTIVE, PENDING_REVIEW, DELETED). Directives: camelCase (@deprecated, @skip, @include). Query/Mutation root type names are conventionally Query and Mutation.

No. All parsing and linting runs entirely in your browser using JavaScript. Your GraphQL schema — which may describe your data model and API surface — never leaves your machine.