material_set

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

Annotations already declare a non-read-only, non-destructive, closed-world mutation, so the safety profile is covered. The description adds a concrete value-format example but says nothing about whether changes are undoable, what happens with invalid property labels, or whether omitted surfaces/properties are preserved.

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?

A single front-loaded sentence with an illustrative example; nothing extraneous. The example partly duplicates the schema's property description, keeping it short of a 5.

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 nested-object mutation tool with no output schema, the description is minimally adequate but omits the key operational context: whether it returns anything, whether changes apply to the given node only, and what happens on partially invalid input.

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 baseline is 3. The example values ('#802020', 0.3) illustrate the property-value forms already documented in the schema, adding marginal clarity but no new semantics about the node or surfaces parameters.

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 names a specific verb ('Changes') and resource ('material properties') and gives a concrete example payload. It does not distinguish this from the sibling material_list, so the agent must infer that this is the write counterpart.

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?

Usage is only implied: it is the tool that writes material properties, versus material_list which presumably reads them. There is no statement of when to use it, prerequisites (e.g. a target node must exist), or what to do instead for other material operations.

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