assign_material_faces

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

With no annotations, the description carries the full burden and does well: it discloses that a slot is auto-added when missing, that unselected faces keep their material, and the performance cost per material. It omits permissions/error behavior and whether the operation is reversible, so not a 5.

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?

Front-loads the core action before the draw-call caveat and the `where` grammar. Dense but every sentence conveys usable information; only minor tightening possible.

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 3-param mutation tool with no annotations and no output schema, the description covers action, side effects, prerequisites, and the filtering grammar. It stops short of describing failure modes (nonexistent material/object) or response shape.

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 fully documents the complex `where` parameter (normal/angle, axis ranges, box, area, index, empty/null semantics), leaving only the self-evident `object` and `material` names unexplained.

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+resource: 'Put an existing material on the picked faces of one mesh.' It also distinguishes itself from the sibling set_material by noting the material must already exist and instructing to create it first.

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?

Explicit prerequisites and routing: create the material first with set_material, and inspect with mesh_info before picking faces. It also gives a when-to-care condition (keep material count low due to per-material draw calls).

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