Skip to content

JSON Schema & Registry

JSON Schema#

Using the default Huma config (or manually via the huma.SchemaLinkTransformer), each resource operation returns a describedby HTTP link relation header which references a JSON-Schema file. These schemas use the config.SchemasPath to serve their content. For example:

HTTP Response
Link: </schemas/Note.json>; rel="describedby"

Object resources (i.e. not arrays or simple scalars) can also optionally return a $schema property with such a link, which enables the described-by relationship to outlive the HTTP request (i.e. saving the body to a file for later editing) and enables some editors like VSCode to provide code completion and validation as you type.

	"$schema": "http://localhost:8888/schemas/Note.json",
	"title": "I am a note title",
	"contents": "Example note contents",
	"labels": ["todo"]

Operations which accept objects as input will ignore the $schema property, so it is safe to submit back to the API, aka "round-trip" the data.


The $schema field is incredibly powerful when paired with Restish's edit command, giving you a quick and easy way to edit strongly-typed resources in your favorite editor.

Schema Registry#

Huma uses a customizable registry to keep track of all the schemas that have been generated from Go structs. This is used to avoid generating the same schema multiple times, and to provide a way to reference schemas by name for OpenAPI operations & hosted JSON Schemas.

The default schema implementation uses a map to store schemas by name,generated from the Go type name without the package name. This supports recursive schemas and generates simple names like Thing or ThingList.

Schema Names

Note that by design the default registry does not support multiple models with the same name in different packages. For example, adding both foo.Thing and bar.Thing will result in a conflict. You can work around this by defining a new type like type BarThing bar.Thing and using that instead, or using a custom registry naming function.

Custom Registry#

You can create your own registry with custom behavior by implementing the huma.Registry interface and setting it on config.OpenAPI.Components.Schemas when creating your API.

Dive Deeper#