Which spirits is the Greater Key of Solomon actually calling on?

It doesn’t read like a catalogue of named spirits in the way the Ars Goetia does. Many conjurations address spirits broadly and command them through divine names and religious authority, rather than naming one specific spirit for each operation. So calling them all demons, or all planetary spirits, would be more definite than the text supports.

The planetary material is relevant, especially for the pentacles and their timing, but that alone doesn’t tell you that every spirit being addressed belongs to a planetary category. Details also vary between editions and translations, so it helps to check which version you’re reading.

I’d separate the ritual’s framework from the identity of the spirit. The text draws on divine names, angels, and planetary correspondences, while some conjurations address spirits without giving an individual name. That can make the language sound like it is aimed at a specific class of hostile beings, but it doesn’t establish that every addressee is chthonic or demonic.

For a close reading, note who or what each passage explicitly names, then keep that separate from what the pentacle or planetary timing is meant to do. The grimoires aren’t always tidy or consistent about these categories.