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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the description's burden is lower. It adds that the tool returns ZIP code(s) and distance, but does not clarify units or how multiple results are handled. It does not contradict 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?

A single, front-loaded sentence with no fluff. It states the core action and output concisely, making it easy to parse quickly.

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 tool with three parameters and no output schema, the description is minimal. It lacks details on the output structure, distance units, and the meaning of count. While annotations cover safety, an agent would need to guess on how to interpret the response, which is a notable gap.

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 description mentions 'latitude/longitude' which maps to lat and lon parameters, but it does not explain the 'count' parameter at all. Since schema coverage is 0%, the description should clarify count's role (e.g., number of nearest ZIPs to return), which it omits. Minimal added value beyond the schema.

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 performs reverse geocoding from latitude/longitude to nearest US ZIP code(s), with distance. It distinguishes from siblings like zip_lookup (which likely takes a ZIP code) and zips_in_radius (which takes a radius), making its purpose specific and 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?

There is no guidance on when to use this tool versus alternatives. It does not mention scenarios like 'use when you have coordinates and need ZIP' or contrast with zip_distance or city_zips. The agent must infer usage from the name and description alone, which is insufficient.

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