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 HTTP endpoint, even for read-only operations. All endpoints accept and return only JSON serialized content.

Entity Endpoints/Actions

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

entities (ident)

Top-level entity actions (resulting in edits):

create (new rev)
update (new rev)
split (remove redirect)

On existing entity edits (within a group):


An edit group as a whole can be:


Other per-entity endpoints:

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


All mutating entity operations (create, update, delete) accept a required editgroup_id query parameter. Editgroups (with contextual metadata) should be created before starting edits.

Related edits (to multiple entities) should be collected under a single editgroup, up to a reasonable size. More than 50 edits per entity type, or more than 100 edits total in an editgroup become unwieldy.

After creating and modifying the editgroup, it may be "submitted", which flags it for review by bot and human editors. The editgroup may be "accepted" (merged), or if changes are necessary the edits can be updated and re-submitted.

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. New tokens can be generated in the web interface.

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.