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

Annotations already declare this as read-only, idempotent, and non-destructive, so the behavioral bar is lower. The description adds the internal two-step behavior of geocoding before weather lookup, but does not disclose failure modes such as invalid ZIPs, unmatchable coordinates, or response behavior. No contradictions 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?

A single, front-loaded sentence that states the input, the resolution mechanism, and the return value. There is no redundant or filler text.

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 simple read-only tool with strong annotations, the schema plus description are mostly adequate for invocation. However, there is no output schema and no description of return structure, invalid-input handling, or what 'current weather' contains, leaving some ambiguity for the agent.

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 description coverage is 0%, so the description must compensate. It only reinforces that zip_code is a US ZIP, adding little beyond the parameter name. It does not explain the units parameter, ZIP format expectations, or how defaults behave.

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 states a clear verb-resource pair: resolve a US ZIP to coordinates and return current weather. It differentiates itself from generic weather_current by explicitly noting the ZIP-to-coordinates resolution step.

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?

It implies usage whenever a US ZIP is known and current weather is needed, but it never names alternatives like weather_current or geo_zip_lookup, nor does it explain when not to use this tool. The context is clear but no exclusions or alternatives are provided.

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