The Administrator Reference Manual (ARM) for Kea is the authoritative reference for Kea commands and usage. It is published in both .html and .pdf formats.
The Kea Messages Guide
The Kea Developer Guide
The Kea Developer Guide is intended for existing or prospective Kea developers and contributors, and provides information needed to extend and maintain Kea source code. This guide is a living document for the current development version.
If you wish to write hook code - the code that is loaded by Kea at run-time and modifies its behavior - you should read the Hooks Developer's Guide section.