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

Annotations already indicate readOnly, idempotent, and non-destructive behavior. The description adds valuable behavioral context beyond that: it explains the conditional return of CSA BASIC percentiles versus the always-available public safety summary, specifies the metrics included, and clarifies interpretation ('Higher BASIC percentiles = worse record'). No contradiction with annotations.

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 description is front-loaded with the core purpose, then efficiently covers return modes, example use cases, and interpretation guidance. The example-question list is slightly long but each item is decision-relevant, and no sentence is redundant.

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 compensates by describing the two possible return forms, the data contained in the safety summary, and how to interpret the metrics. It does not cover error cases or mention alternative fmcsa tools, but for a single-parameter read-only lookup the essential information is present.

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 schema has 0% description coverage, so the description must compensate, but it only repeats that the tool works 'by DOT number.' This adds little beyond the parameter name and the schema's integer/exclusiveMinimum constraints. It does not explain how to obtain or format a DOT number or any additional semantic guidance.

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 and resource: 'Get safety information for a trucking company by DOT number.' The description further clarifies the two possible return types, which helps differentiate it from generic carrier lookups. However, it does not explicitly distinguish itself from sibling tools like fmcsa_carrier_lookup or fmcsa_carrier_authority.

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?

Provides clear usage context through example questions like 'is this carrier safe?' and 'how many crashes?' and explicitly says 'or any trucking safety evaluation.' It does not state when not to use it or mention alternative tools, so it lacks explicit exclusions and sibling routing.

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