Create walls, lights and other canvas elements

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description attributes a key non-schema detail: 'One bad entry creates nothing' (atomicity), which prevents partial writes. It also adds a permission gate and the 200-element batch limit. Annotations only carry false hints, so this add value.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The text is dense but organized as a list separated by semicolons, with the most useful batch/permission facts at the end. All content is functional and none is redundant with the schema.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a complex multi-type batch-creation tool, this is enough: per-type structures, atomicity, permission requirement, and size cap. Lack of output details is minor because no output schema exists and the rule is not to duplicate output definitions; still missing are return-value or confirmation semantics.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description substantially enriches the schema. For each elementType it gives precise field layouts (e.g., Wall: c [x0,y0,x1,y1], door state options, light/sound fields, tile texture src, drawing shape). This goes far beyond the schema's generic 'Foundry fields' placeholder.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: create canvas elements, up to 200, on a scene, and lists the six element types. It clearly stands apart from sibling update-canvas-elements, delete-canvas-elements, and list-canvas-elements.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives batch size, one-type-per-call, and permission prerequisites ('Needs the level change for scenes'), plus an atomic failure mode. It does not explicitly spell out 'use update for existing elements' but the naming makes it obvious.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.