All API endpoints conform to the pattern ''[PREFIX]LETTER[/ZETTEL-ID]'', where:
; ''PREFIX''
: is the URL prefix (default: ""/""), configured via the ''url-prefix'' [[startup configuration|00001004010000]],
; ''LETTER''
: is a single letter that specifies the resource type,
; ''ZETTEL-ID''
: is an optional 14-digit string that uniquely [[identifies a zettel|00001006050000]].

The following letters are currently in use:

|= Letter:| Without zettel identifier | With [[zettel identifier|00001006050000]] | Mnemonic
| ''a'' | POST: [[client authentication|00001012050200]] | | **A**uthenticate
|       | PUT: [[renew access token|00001012050400]] |
| ''r'' |  | GET: [[references|00001012053800]] | **R**eference
| ''x'' | GET: [[retrieve administrative data|00001012070500]] | | E**x**ecute
|       | POST: [[execute command|00001012080100]]
| ''z'' | GET: [[list zettel|00001012051200]]/[[query zettel|00001012051400]] | GET: [[retrieve zettel|00001012053300]] | **Z**ettel
|       | POST: [[create new zettel|00001012053200]] | PUT: [[update zettel|00001012054200]]
|       |  | DELETE: [[delete zettel|00001012054600]]

The full URL will contain either the ""http"" oder ""https"" scheme, a host name, and an optional port number.

The API examples will assume the ""http"" schema, the local host ""127.0.0.1"", the default port ""23123"", and the default empty ''PREFIX'' ""/"".
Therefore, all URLs in the API documentation will begin with ""http://127.0.0.1:23123/"".