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

With readOnlyHint and openWorldHint already declared, the description adds genuinely new behavioral facts: the upstream source (FMCSA) and, importantly, the x402 payment model — $0.02 USDC per call, charged only on success. That cost/charging semantics is not derivable from annotations and materially affects invocation. It does not address what happens when neither identifier is supplied, which is a minor gap.

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 sentences: purpose and scope first, then source and price. Every clause carries information an agent needs — identifiers, returned fields, data provenance, cost — with no filler or repetition.

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?

There is no output schema, so the description correctly enumerates the fields returned (authority, insurance, safety rating, fleet size, OOS rates), and it discloses the price and billing trigger. The one missing piece is that neither parameter is marked required while at least one identifier is clearly needed, which the description never resolves.

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% and both parameters are documented as alternatives, so the schema carries the semantic load. The description's 'by USDOT or MC number' restates that relationship but adds no format, validation, or precedence guidance (e.g., what happens if both are passed). Baseline 3 is correct here.

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?

Specific verb+resource ('Check a US motor carrier by USDOT or MC number') with the returned data fields enumerated: operating authority, insurance, safety rating, fleet size, out-of-service rates. The domain is unambiguous against siblings like check_product_recalls or verify_healthcare_provider, so an agent can route correctly 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 description gives a clear trigger context (a US motor carrier identified by USDOT or MC number) and names the accepted identifier types, which tells the agent when this tool applies. It stops short of stating exclusions or alternatives, but no sibling overlaps this domain enough to require them.

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