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

Annotations already establish read-only, idempotent, and non-destructive behavior. The description adds valuable behavioral details: 'Returns up to 10 results' and 'case-insensitive' search, which are not present in the annotations. No contradictions detected.

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, but it redundantly repeats the same sentence under 'When to use' and the parameter details mirror the schema. This unnecessary duplication prevents a higher conciseness score.

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 search tool with no output schema, the description provides essential context: result cap (10) and the nature of results (city and state details). While more detail on response fields would be helpful, the low complexity and strong annotations make this sufficiently complete.

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 fully describes the 'search' parameter with identical wording. The description's parameter section adds nothing beyond the schema. Baseline 3 applies since schema coverage is 100%.

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 clearly states the tool's function: 'Search US zip codes by zip code, city, or state name.' It specifies the resource (US zip codes), the action (search), and the input modes, distinguishing it from sibling tools like fetch_states and fetch_areacodes.

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 'When to use' section reiterates the purpose but does not explicitly contrast with alternatives or mention exclusion conditions. Usage context is clear, but no specific guidance is given about when to prefer this tool over other fetch_* tools, making it implied rather than explicit.

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