paint_faces

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

No annotations are provided, so the description carries the full burden. It discloses the essential behavioral trait that this writes vertex colour data and only on picked faces (implying a selection prerequisite), but says nothing about persistence, reversibility/undo, or what happens to existing vertex colours on those faces.

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, zero filler, with the core action and scope front-loaded before the format and use-case details.

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 mutation tool with no annotations and no output schema, the description covers the action, the colour format, and the selector semantics, but omits the `attribute` parameter's meaning and any statement about whether painting is destructive or reversible.

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 coverage is 0%, so the description must compensate. It does well for `color` ('#rrggbb' or [r,g,b]) and `where` (delegating to select_faces and listing the selector kinds: normal, x/y/z ranges, box, area, index). `object` is self-evident, but `attribute` (default 'Color') is never explained — that is the remaining gap.

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 ('Paint vertex colour on the picked faces') with the scope qualifier that it operates only on already-selected faces, which distinguishes it from sibling select_faces (selection) and assign_material_faces (material-based colouring). An agent can tell what it does 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 context cue ('For stylised models that use vertex colours instead of textures') and routes the agent to select_faces for the `where` semantics, implying a prior selection step. It does not, however, explicitly name assign_material_faces or set_material as the alternative for textured models, so the routing is implicit rather than stated.

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