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

Annotations already declare readOnlyHint and openWorldHint, so the description is free to add the genuinely new information: a metered cost of $0.002 USDC per successful call via x402, and that failed calls are not charged. That is real decision-relevant behavior (billing model, payment rails) not present in structured fields; only per-call limits or latency expectations are absent.

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 identification and source come first, then the caveat, then the pricing — a sensible front-loading order. The field enumeration makes the first sentence long, but every clause (source, fields, scope caveat, price) carries information an agent needs.

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 one-parameter lookup with an output schema and annotations, the description supplies everything left uncovered: data provenance (data.transportation.gov Company Census File), what is explicitly out of scope, and the payment model. Nothing needed 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 coverage is 100% with a single required 'dot' string fully documented as digits-only, 1–8 digits. The description only restates 'by USDOT number' without adding format, normalization, or fallback guidance, so it neither compensates nor detracts — the schema does the work.

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?

Names a specific verb+resource ('FMCSA carrier census record by USDOT number') and enumerates the returned fields (legal name, address, power units, drivers, status, registration dates). It also bounds the scope against adjacent FMCSA data ('Census file, not live inspection or crash data'), so an agent can distinguish it from inspection/crash or complaint sources without opening the 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?

The negative scoping ('not live inspection or crash data') tells the agent when this source is inappropriate, and the pricing line clarifies the cost of a call. However, no sibling is named — notably gov_fmcsa_household_goods_complaints — and there is no explicit statement of when to prefer this over another carrier/complaint source.

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