paint_faces

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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the agent knows this mutates state. The description adds that no material/texture is created and that colour lands on 'picked faces', but it never says whether existing vertex colours are overwritten or appended, nor whether a selection must exist first — the most important behavioral risk for a destructive paint tool.

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?

Two tight sentences, front-loaded with the action and the key differentiator ('without a material or a texture'), then the colour format and the pointer to select_faces. No filler.

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 4-parameter destructive mutation with no output schema and 0% schema coverage, the description covers the colour format and the predicate reference but omits overwrite semantics, required selection state, and the meaning of `attribute`/`object`. Adequate to invoke, not complete.

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?

Schema description coverage is 0%, so the description carries the burden: it documents the `color` format ('#rrggbb' or [r,g,b]) and points to select_faces for the `where` predicate values. However, it never explains `object` or `attribute` (default 'Color'), leaving two of four parameters undocumented in both schema and prose.

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?

States a specific verb and resource ('Colour faces ... vertex colour on the picked faces') and immediately carves out its niche by saying it works 'without a material or a texture', which distinguishes it from siblings like assign_material_faces and set_material. An agent can pick it without opening the schema.

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?

Gives a clear use condition ('For stylised models that use vertex colours instead of textures') and routes the agent to select_faces for the `where` semantics. It does not explicitly say when NOT to use it versus assign_material_faces/set_material, so no exclusions are stated.

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