The fatcat HTTP API is mostly a classic REST CRUD (Create, Read, Update, Delete) API, with a few twists.

A declarative specification of all API endpoints, JSON data models, and response types is available in OpenAPI 2.0 format. Code generation tools are used to generate both server-side type-safe endpoint routes and client-side libraries. Auto-generated reference documentation is, for now, available at

All API traffic is over HTTPS; there is no insecure HTTP endpoint, even for read-only operations. To start, all endpoints accept and return only JSON serialized content.

Entity Endpoints/Actions

Actions could, in theory, be directed at any of:

entities (ident)

A design decision to be made is how much to abstract away the distinction between these three types (particularly the identifier/revision distinction).

Top-level entity actions (resulting in edits):

create (new rev)
update (new rev)

On existing entity edits (within a group):


An edit group as a whole can be:


Other per-entity endpoints:

match (by field/context)
lookup (by external persistent identifier)


All mutating entity operations (create, update, delete) accept an editgroup_id query parameter. If the parameter isn't set, the editor's "currently active" editgroup will be used, or a new editgroup will be created from scratch. It's generally preferable to manually create an editgroup and use the id in edit requests; the allows appropriate metadata to be set. The "currently active" editgroup behavior may be removed in the future.

Sub-Entity Expansion

To reduce the need for multiple GET queries when looking for common related metadata, it is possible to include linked entities in responses using the expand query parameter. For example, by default the release model only includes an optional container_id field which points to a container entity. If the expand parameter is set:

Then the full container model will be included under the container field. Multiple expand parameters can be passed, comma-separated.

Authentication and Authorization

There are two editor types: bots and humans. Additionally, either type of editor may have additional privileges which allow them to, eg, directly accept editgroups (as opposed to submitting edits for review).

All mutating API calls (POST, PUT, DELETE HTTP verbs) require token-based authentication using an HTTP Bearer token. If you can't generate such a token from the web interface (because that feature hasn't been implemented), look for a public demo token for experimentation, or ask an administrator for a token.

Autoaccept Flag

Currently only on batch creation (POST) for entities.

For all bulk operations, optional 'editgroup' query parameter overrides individual editgroup parameters.

If autoaccept flag is set and editgroup is not, a new editgroup is automatically created and overrides for all entities inserted. Note that this is different behavior from the "use current or create new" default behavior for regular creation.

Unfortunately, "true" and "false" are the only values acceptable for boolean rust/openapi2 query parameters

QA Instance

The intent is to run a public "sandbox" QA instance of the catalog, using a subset of the full catalog, running the most recent development branch of the API specification. This instance can be used by developers for prototyping and experimentation, though note that all data is periodically wiped, and this endpoint is more likely to have bugs or be offline.