A willing agent (fāʿil mukhtār) is one whose actions are not explained solely as a compulsory consequence of essence. The particular act is attributed to power and will.
Calling God a willing agent does not imply human deliberation, hesitation, changing information or successive decisions. These are limitations of created agents.
The theological point is to distinguish volition from newly originated willing: an act can be voluntary even while the divine attribute of will is held to be eternal.