zip_by_city

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

Annotations already declare readOnly, idempotent, non-destructive, open-world. The description adds nothing beyond that — no note on whether results are one code or many, whether partial matches are returned, or what the default country behavior yields. Adequate given annotation coverage, but no added disclosure.

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?

One short, front-loaded sentence with no waste. It is however so terse that it leaves room unused rather than being optimally structured for an agent.

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 3-param lookup with full schema coverage and annotations, this is minimally sufficient. Missing niceties include whether multiple codes may return and how the optional country interacts with the state abbreviation.

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 100% and includes the useful 'State abbreviation (e.g. CA, NY)' and country default. The description restates city/state without adding format rules or clarifying the country parameter's effect. Baseline 3 applies since the schema does the work.

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?

Specific verb+resource ('Look up zip/postal codes') with an explicit scope ('for a city and state'). It's clearly distinguishable from plausible siblings like zip_lookup (reverse direction) or auspost_get_postcode, though the description doesn't name any of them.

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 'city and state' phrasing implies the forward direction (place → codes) rather than the reverse, which is the main usage discriminator against zip_lookup. But there's no explicit statement of when to use this vs. postcode_lookup or zip_lookup, and no exclusions.

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