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

Annotations already establish readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds meaningful behavioral detail by stating that it returns a comparison table and enumerating the exact data dimensions: fleet size, driver count, safety rating, crash history, BASIC safety scores, authority status, insurance, and out-of-service rates. This is helpful since no output schema is provided.

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 core action and output are front-loaded in the first sentence, and the second sentence follows with the return format and then example queries. It is efficiently written, though the five example phrasings are somewhat redundant and could be trimmed without losing clarity.

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 single-parameter tool with full schema coverage and safety annotations, the description is largely complete: it states the input scope, the decision use case, and the returned comparison dimensions. It does not cover data freshness or how incomplete records are handled, but that is a minor gap given how much is already explained.

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?

The input schema already documents dot_numbers thoroughly, including the 2-5 range and accepted formats (array or comma-separated string), so schema coverage is 100%. The description reinforces the 2-5 carrier range but adds no new parameter-level semantics beyond what the schema provides.

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 opens with a specific verb and resource: 'Compare 2 to 5 trucking companies side by side on safety, fleet size, insurance, and authority.' This clearly distinguishes it from sibling tools like fmcsa_carrier_lookup, fmcsa_carrier_search, and fmcsa_safety_scores, which are single-carrier or score-specific operations. The tool's purpose as a multi-carrier comparison is unambiguous.

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 provides clear usage context with concrete question examples such as 'which carrier is safer?' and 'compare these trucking companies,' and closes with 'or any carrier vetting decision.' It does not explicitly name alternative tools or state when not to use it, but the 'use for questions like...' framing gives an agent solid selection guidance.

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