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

Beyond the annotations (readOnly/idempotent/non-destructive), the description discloses that the call is paid at a flat price, that an unregistered hash returns registry_unavailable and is not billed, and that an unknown USDOT number is a free not_found — cost and failure-mode behavior an agent cannot get from the schema. It also explains the integrity contract: record_hash is SHA-256 over canonical JSON excluding record_hash and verify_url, and verify_url re-confirms issuance for free.

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?

It is front-loaded with identity and purpose, then contents, then scope disclaimers, then integrity/billing — a sensible order. The long parenthetical enumerations of returned fields are dense but earn their place because there is no output schema; only the repeated negation clauses ('not a score', 'not legal advice', 'not a statement that choosing a carrier was reasonable') could be tightened.

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?

With no output schema, the description carries the full burden of describing returns and does so field-group by field-group, plus explicitly notes that safety_tier_derived is excluded. Billing, error cases, hash verification, and the 'Unrated is reported as exactly that' edge case are all covered, leaving nothing material an agent needs before calling.

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 description coverage, the schema already defines usdot_number as the canonical FMCSA identifier. The description adds only the behavioral note that an unknown USDOT yields a free not_found, which is about outcomes rather than the parameter itself, 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?

The description states a specific resource: a dated, hashed record of FMCSA carrier data assembled for a broker's vetting file, and enumerates exactly what it contains (profile, SMS, crashes, insurance continuity, authority events, review_factors). The line 'It is a record, not a score' sharply distinguishes it from any derived-rating tool. It stops short of naming which sibling to use instead, so it lands at 4 rather than 5.

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 through the 'broker's carrier-vetting file' framing and the instruction to keep the record and later GET verify_url, which tells an agent where this fits in a workflow. However, there is no explicit when-to-use versus when-not guidance and no named alternative among the many sibling lookup/screening tools, so the agent must infer selection from the field list alone.

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