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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description adds important context: it is a paid x402 tool costing $0.002 USDC per successful call, failed calls are free, and it returns label code numbers as written rather than artwork or ERG entries. It does not disclose rate limits or data freshness.

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 three efficient sentences, front-loading the purpose, then clarifying output limits, then stating pricing. No sentence is redundant, and the pricing detail is relevant to invocation.

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 simple one-parameter read-only lookup with an output schema, annotations covering safety and open-world behavior, and a clear source table, the description supplies enough context: source, input forms, returned fields, exclusions, and cost model.

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 coverage is 100%, so the schema already documents the single q parameter as a 4-digit UN number or 3–60 character name fragment. The description repeats the example and input forms without adding matching semantics or normalization rules, making 3 the appropriate baseline.

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 resource and scope: placard/label codes for a hazardous material from the US DOT table by UN number or name fragment. It also enumerates returned fields (label codes, hazard class, packing group), but it does not explicitly differentiate itself from the most relevant sibling, logistics_un_dangerous_goods.

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 implied by the input forms and by the exclusion of placard artwork and emergency response guide entries. However, it gives no explicit when-to-use guidance relative to the many sibling tools, especially logistics_un_dangerous_goods.

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