set_material_layer_parameter

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

Annotations cover the safety profile (readOnly=false, destructive=true, idempotent=true), so the bar is lower, yet the description adds the key non-obvious trait that the engine's success flag is unreliable and re-reading is required. It does not clarify what the destructive overwrite actually replaces per layer, keeping this short of 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-loaded with the core action and scope, then the sibling differentiation, then the verification caveat. Every sentence carries distinct value, including the Returns line, which compensates for the missing output schema.

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 destructive, 5-required-parameter mutation with full schema coverage and no output schema, the description covers what it writes, where it is scoped, the sibling tradeoff, the unreliable success signal, and the return shape. Nothing an agent needs to invoke it correctly is missing.

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 100%, so the schema already documents every parameter (value, layer_index, parameter_name, parameter_type, material_instance_path). The description reinforces the zero-based layer_index scoping but adds no syntax or format beyond the schema; baseline 3 is correct.

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 gives a precise verb+resource ('Write a scalar/vector/texture parameter scoped to ONE layer of a layered material instance') and immediately names the sibling it differs from (set_material_instance_param_override). An agent can distinguish this from the Global-association setter without opening either 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?

It states the selecting condition explicitly ('scoped to ONE layer... so each layer of a blend keeps its own tiling, tint or texture') and names the alternative plus the exact failure mode of using the wrong one ('would hit the wrong slot on a layered material'). It also prescribes follow-up verification with get_material_layer_parameter.

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