Cantrip Limitations - Druidcraft, Mending, Thaumaturgy

Druidcraft - Known Limitations

RAW:
Whispering to the spirits of nature, you create one of the following effects within range:

• You create a tiny, harmless sensory effect that predicts what the weather will be at your location for the next 24 hours. The effect might manifest as a golden orb for clear skies, a cloud for rain, falling snowflakes for snow, and so on. This effect persists for 1 round.
• You instantly make a flower blossom, a seed pod open, or a leaf bud bloom.
• You create an instantaneous, harmless sensory effect, such as falling leaves, a puff of wind, the sound of a small animal, or the faint odor of skunk. The effect must fit in a 5-foot cube.
• You instantly light or snuff out a candle, a torch, or a small campfire

Rulings:

1. The weather-predicting ability is relatively low-resolution and may not show shifts in weather, just the prevailing conditions over the next 24 hours. For example, if it's going to be sunny but rain for less than an hour, the caster might get the sunny indicator despite the rain expected.
2. The weather-predicting ability doesn't account for unnatural changes to the environment (spells cast that might change the weather or other magical effects). It may show what the weather would be if not affected by magic rather than what it actually turns out to be.
3. The plant-manipulation effect is not illusory, but will have no mechanical effect beyond appearances (DM discretion). For example: Several castings might cause vines that are already nearby to grow over fallen rocks. These would be no harder to dislodge, but they would appear to have been in place longer and might be harder to notice.

Mending - Known Limitations

RAW:
This spell repairs a single break or tear in an object you touch, such as a broken chain link, two halves of a broken key, a torn cloak, or a leaking wineskin. As long as the break or tear is no larger than 1 foot in any dimension, you mend it, leaving no trace of the former damage. This spell can physically repair a magic item or construct, but the spell can't restore magic to such an object.
Rulings:

1. Multiple separate breaks can be repaired by multiple castings.
2. Larger breaks may be repaired with multiple castings in some circumstances, usually around being able to secure the pieces while it happens (DM discretion).
3. The parts of the object need to be present for it to be mended. If parts are missing, mending may leave gaps where the missing parts belong or fail altogether.

Thaumaturgy in combat

RAW: "You manifest a minor wonder, a sign of supernatural power, within range."
Ruling: This is, by its very nature, going to be pretty subjective and require a lot of spot-ruling on the part of the DM. Clever use of it will generally aid in other efforts (lower DC to Intimidate, for example) but because it doesn't have "hard and fast" rules its usefulness in a given situation will be hard to properly gauge.