We all know that a lot of structures in Minecraft have their own rules about spawning, but there's no way to tell exactly where these rules stop applying. How far from a nether fortress intersection can wither skeletons spawn? How close can I get to this village with bad omen without causing a raid? With Paint's Structure Bounds, I've made it easy!
While in a detectable structure, hold any kind of arrow in your main hand or offhand. You'll see it says "Inside:" on your actionbar, followed by what the structure is. You'll also see particles around you, showing you which blocks in your 3x1x3 area are technically in the structure. Green dust means it's in, ash particles means it's out.

Did you know that the treasure rooms under desert pyramids and jungle temples are not technically part of their structure, but igloo basements are? Did you know that apart from guardians, no hostile mobs can spawn in ocean monuments, even if it's totally drained and dark? Did you know that the "legs" of an ocean monument aren't part of the structure, but above the slopes are, up to the level of the ocean monument's highest block? So much to discover!
You might see this and be a little confused:

The reason you can see nine ash cloud particles (showing that those blocks are not in the structure) is because particle clouds are testing the air blocks that they are in, while you on a grass path, are testing the path block itself. It turns out that Minecraft is really picky about where is and isn't a village!
There are no ticking functions and it's multiplayer friendly.
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