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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered. The description adds genuinely new context: this is a closed, built-in set of materials with defined defaults, telling the agent no external data source is consulted.

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?

Very short and front-loaded, with the material list up front. The Chinese and English sentences are near-duplicates, a minor redundancy that costs a little efficiency but keeps the definition compact.

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 zero-parameter enumeration tool, the description is complete: it names the domain, the covered materials, and the existence of defaults. An output schema exists, so return-value structure need not be explained.

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 tool takes zero parameters, which is the baseline 4 case. The description correctly signals a no-argument call by describing the result set rather than any input.

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+resource (list built-in material density table) and enumerates the actual materials covered (Q235/Q355, 304, 316, aluminum, copper) plus the presence of defaults. An agent can immediately tell this apart from the sibling weight_calculate, which computes rather than lists.

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 a reference lookup whose natural role is to supply density values before calling weight_calculate. There is no explicit when-to-use, when-not-to-use, or naming of an alternative (e.g., custom materials). Adequate but with a clear gap.

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