zip_lookup

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

No annotations are provided, so the description carries the full burden. It discloses that the tool returns region, city, and work schedule, which is useful. However, it does not mention error behavior when a postal code is invalid or not found, nor any side effects, rate limits, or authentication requirements. For a simple lookup this is acceptable but still leaves gaps.

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 a single, clear sentence that front-loads the key information (what the tool does and what it returns). There is no redundancy or filler.

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 one simple parameter and no output schema, the description sufficiently informs an agent of the expected output fields. It lacks explicit handling of edge cases like invalid codes, but for a lookup of this nature, it is largely complete. The presence of sibling tools with distinct purposes reduces the need for elaborate guidance.

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 coverage is 100% and the parameter is fully described in the schema (postal code, 6 digits, pattern). The description adds no additional meaning about the parameter itself; it only describes the output. Per the rubric, a baseline of 3 is appropriate when schema already covers parameters.

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 a specific action (lookup) and resource (postal code), listing the returned data fields (region, city, work schedule). It is easily distinguishable from sibling tools like track, calculate, and get_offices, which have different purposes.

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 description implies the tool should be used when a postal code is given and region/city/schedule info is needed, but it does not explicitly state when to use it over alternatives or mention any exclusions. The purpose is clear enough, but there is no direct guidance on selection criteria.

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