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

No annotations are provided, so the description carries the behavioral burden. It usefully discloses that results are approximate, the scope is Australian postcodes, and 'PRO' suggests a tier/subscription distinction, but it omits auth behavior, error handling, and invocation constraints beyond the schema.

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 very short and front-loads the core purpose. 'PRO.' is slightly cryptic, but the overall structure is efficient with no padding.

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 distance calculation, the description conveys the key return concept (approximate km) despite no output schema. However, it leaves input format and behavior for invalid or non-Australian postcodes unspecified, and does not relate the tool to its siblings.

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 only 33%, with access_token documented in the schema. The description clarifies that from/to are Australian postcodes, adding meaning beyond the bare parameter names, but it does not specify postcode format or further access_token behavior.

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 operation and resource: approximate distance in km between two Australian postcodes. It is specific enough to distinguish from a simple postal lookup, though it does not explicitly name sibling tools or their differences.

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 postal_lookup or batch_postal, nor any stated exclusions or prerequisites. The only usage signal is that it applies to two Australian postcodes.

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