set_face_material_index

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

No annotations provided, so the description must fully disclose behavior. It explains parameters but does not mention error behavior, reversibility, or whether the operation is destructive. Missing details like what happens if material_index does not exist.

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 description is concise: one initial sentence followed by a clear parameter list. Every sentence adds value without redundancy.

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?

Given no output schema and no annotations, the description covers parameter semantics but lacks information about return values, error handling, or side effects. For a small tool, it is mostly complete but could include behavioral context.

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 adds significant detail beyond the schema: face_indices is explained as 'comma-separated face indices, or 'all'', and material_index is clarified as '0-based; material must already exist'. With 0% schema coverage, the description fully compensates.

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 clearly states 'Assign a material slot to specific faces (for multi-material objects).' It uses a specific verb and resource, and distinguishes from sibling tools like assign_material which typically assign a whole material to an object.

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?

The description includes 'for multi-material objects' which implies when to use, but does not explicitly state when not to use or provide alternatives. It gives clear context but lacks exclusions.

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