calculate_zip_code_distance

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

Beyond the readOnlyHint, idempotentHint, and destructiveHint annotations, the description discloses that the tool supports Haversine or Vincenty formulas and that it returns origin/destination details and the computed distance. This adds meaningful behavioral context about calculation method and output contents.

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 two concise sentences, starting with the action verb and resource, and includes the key additional information (formulas and return contents) without unnecessary words.

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?

Given the tool's simplicity, full schema documentation, and strong annotations, the description provides sufficient context: it covers the core inputs, method variants, and the nature of the return value. No critical information is missing for an agent to select and invoke this tool correctly.

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 provides descriptions for all four parameters, covering 100% of the parameter semantics. The description does not add parameter-specific details beyond mentioning the formula option, so it does not exceed the baseline set by 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 a specific action ('Calculate the distance') on a specific resource ('two ZIP codes'), and mentions the two formula options. It distinguishes itself from sibling tools like lookup_zip_code and find_zip_codes_in_radius by focusing on direct distance calculation.

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 use case is clear: calculating distance between two ZIP codes. However, there is no explicit mention of when not to use it or explicit alternatives, such as find_zip_codes_in_radius for radius-based searches, which would make it a 5.

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