Third party refers to the developers whom consume it.
Yes I know, I’m a third party developer. However the way ESI router publishes the OpenAPI specification, it only combines it at runtime, sane developers publish specs at build time. See my complaints about it here Https://esi.evetech.net/latest/characters/{character_id}/assets/ returning 404 - #14 by Emotional_Support_Clown
CCP cannot even publish an OpenAPI spec properely.
Also their “status” API doesn’t even reflect the “status” of a down endpoint for routes. They disappear, no status in sight. They disappear from the OpenAPI spec and the status route. See my complaints about that here Https://esi.evetech.net/latest/characters/{character_id}/assets/ returning 404 - #16 by Emotional_Support_Clown.
OpenAPI is also how we third party developers generate client stubs. It’s pretty damn hard to do that when the spec is disappearing in parts. It’s not just “documentation”, it’s for code generation. You think we sit there like a tool hand crafting an API stub and models? Don’t be silly.
If you want me to fill you in on the problems of CCP and API’s, let me know; I got much more complaints.