mat_set_sub_material

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

Annotations already signal mutating/destructive behavior, and the description adds that the tool either creates a new material class or reuses an existing material by name. However, it does not disclose whether an existing sub-material is overwritten, whether reuse is by reference or copy, or what happens if both subClass and sourceMaterial are provided.

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 compact and front-loaded, with the core operation and index meaning stated first. The bilingual repetition is justified for accessibility and adds 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 mutating tool with no output schema, the description covers the essential invocation details: target material, slot index, and both allowed creation/reuse modes. The main gap is the ambiguous relationship between subClass and sourceMaterial when both are supplied, but this does not prevent a capable agent from making a correct first call.

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 schema already documents all four parameters, so the baseline is 3. The description adds meaningful relationship semantics: subClass and sourceMaterial are presented as alternative actions, and the index is explicitly stated as 1-based. It stops short of specifying which parameter takes precedence or that exactly one mode should be supplied.

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: setting a sub-material into a numbered slot of a Multi/Sub-Object material. It also names the two supported modes (create new subClass or reuse sourceMaterial), which clearly differentiates it from sibling tools like mat_set_slot or mat_set_property.

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 clearly implies this is for modifying Multi/Sub-Object materials by sub-slot index, but it does not explicitly say when not to use it or name alternatives. It also leaves the choice between subClass and sourceMaterial as an unqualified 'or' without guidance on which to pick in which scenario.

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