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

With no annotations, the description carries the full burden and largely meets it: it declares the operation is free/never billed, states exactly what is returned (identifiers and a status, no names or addresses), and maps error conditions (unknown docket -> not_found, unreadable -> invalid_arguments). It omits auth requirements and rate limits, so it stops short of a 5.

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?

Front-loaded with the outcome ('Free. Finds the USDOT number...') and every subsequent sentence carries concrete information about formats, return fields, or errors. It is dense and longer than typical, but little of it is waste.

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 tool with no output schema, the description covers input formats, output semantics (authority_holder_usdot_number, usdot_numbers with holder-first ordering and the two-carrier census case, docket_status/status_source provenance), error behavior, and billing — nothing an agent needs 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 0% and the single parameter is undocumented in the schema, so the description must compensate — and it does thoroughly. It enumerates accepted formats ('MC123456', 'MC-123456', 'mc 123456', '123456'), states the bare-number default (taken as MC), and explains zero-padding is ignored because FMCSA files disagree.

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+transformation: it finds the USDOT number for an operating-authority docket number (MC, MX or FF). The scope sentence ('so a broker holding the MC number ... can reach the other tools, which take a USDOT number') distinguishes it from siblings like lookup_carrier or search_carriers that consume a USDOT number directly.

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?

Clearly sets the situation for use: an agent has an MC/docket number and needs a USDOT number to call other tools. That routing context is explicit, though no sibling is named as a direct alternative and no 'do not use when' case is stated.

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