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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavior: it is free ('costs no units') and returns a binary admissible/refusal verdict against a strict reader, which is not captured in the structured fields.

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?

Two tight clauses with the verb front-loaded and zero filler; the cost note follows the outcome statement and earns its place by informing invocation decisions.

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?

An output schema exists so the verdict format need not be explained, and annotations carry the safety profile. Combined with the cost and strictness notes, an agent has enough to invoke it correctly, though the meaning of 'strict reader' remains slightly opaque.

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?

With a single parameter at 100% schema coverage, the schema already documents that the material is an inline JSON object. The description adds nothing about the expected document shape or constraints, so the baseline 3 applies.

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 (checks) plus resource (material document) and the outcome form ('admissible, or the refusal'). It is clearly distinguishable from write siblings like material_apply or material_bake, though it never names them explicitly. The 'engine's strict reader' phrasing is somewhat internal jargon.

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?

'Costs no units' implicitly signals this is a free pre-flight validation you can call before material_apply, which is useful implied guidance. However, it never states when-not to use it or explicitly contrasts it with material_cost or material_apply.

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