The KERNAL jump table is documented, and we're formalizing and documenting more of the KERNAL API as we go, including adding accessor routines for useful internal state. For example, we recently added a KERNAL routine to access properties of the most recent disk operation. Vectors, such as the IRQ vector, are accessible via the VECTOR accessor—which was actually in Commodore's original jump table but nobody used it. Memory usage by the KERNAL and BASIC is also documented. And of course all of the hardware registers are documented.
Otherwise no. Old fashioned "magic peeks and pokes" rely on the fact that Commodore is dead and nobody is releasing new versions of the C64 KERNAL. The MEGA65 KERNAL is under active development, and programs must rely on official documented APIs for KERNAL integrations to work with future versions of the platform.
If you have any specific things you need from the KERNAL that are not yet documented, please let me know, so we can consider adding accessors.
