Let's suppose that at the inception of our world the creator god creates a set of rules for pantheons and minor gods, places divine rulership in the hands of a couple underlings he makes, then packs it in for the day (read effectively eternity to everyone else).
The rules are simple enough.
All gods are omniscience at point of ascension or when they pop into existence however they may only disclose knowledge a mortal could concievably know, and when it is knowledge the mortal may not know it must be obfuscated. This can be summarised to No Spoilers unless Riddled. Or the Prophecy Conundrum.
Gods may converse will believers at will, however not directly with non-believers though intermediaries are acceptable. Nor may they directly interfere with the lives of non-believers. (Belief and worship are used separately.)
Belief is defined as an individual choosing to accept the existence of said god AND follow them via explicit verbal agreement. Generally speaking a prayer is considered a temporary form of belief contract. Ultimately this definition is more for mortals though as gods are omniscient and completely aware of mortal beliefs.
A god's power is defined by the number and fervour of their believers.
A god may never lie.
Edit: A god's power is established by their eminent domain. There is a minimum power thresh-hold which is high enough for major works of power but only in a small area. Their eminent domain is established by what people believe they are. For instance a god may wish to be a god of fishermen, but if sailors call on them for help, their eminent domain will move to being for sailors. In terms of localisation, a small god may be able to heal a follower, or protect them from a storm (the follow is considered the local point) but will not be able to change the weather <- eminent domain not large enough to influence that of the local weather god. This example brings up the point that where eminent domains overlap, the god with greater power will have authority.
Breaking the rules is to risk banishment or annihilation. Which are automatically triggered once a proclamation is made by the greater gods.
There's a myriad other rules that were made over time like how afterlives were governed, good behaviour around prophets, and morality but those were the major ones.
I've always been curious. How do you think religion would develop in this world? Do you think it would be widespread -> religion as service/business transaction. Or something else? Could we draw parallels to history on our own planet?