When swallowed by a Giant Toad, you are Blinded and Restrained, both of which give you disadvantage on attacks.
However you also have "total cover against attacks and other effects outside the toad".
The Toad's eyes are outside the Toad, and I certainly don't see anything inside my own stomach. Doesn't this mean you are considered Unseen when swallowed?
The rules on Unseen Attackers and Targets (PHB, p. 194-195) state:
When a creature can't see you, you have advantage on attack rolls against it.
Am I unseen while swallowed?
If this is true, then your disadvantage from being blinded and restrained and your advantage from being unseen cancel out, and an attack against the Toad from within has no advantage or disadvantage. Is this correct?
Best Answer
Neither advantage nor disadvantage
As you say, you have several sources of disadvantage and one source of advantage - being unseen. These cancel, leaving you with neither.
Even if you don’t particularly like this source of advantage, there is a strong argument for advantage from a non-conventional source: every way is toad. If you can just wiggle your sword a little or manage to get your Fire Bolt off, you are bound to hit toad.