get_postal_areas

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

With no annotations, the description carries the full burden. It correctly identifies this as a read-only operation by stating 'look up' and explicitly mentions 'No authentication required'. It also describes the return values. However, it doesn't disclose potential limitations like data freshness or rate limits, which is acceptable for a simple lookup.

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 extremely concise: two sentences that cover the purpose, return values, and authentication requirement. Every word is meaningful, and the structure is front-loaded with the key action and outcome.

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 one-parameter lookup tool without an output schema, the description provides all necessary context: what it does, what it returns, and that it requires no authentication. It is fully complete for an AI agent to correctly select and invoke the tool.

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 100% coverage for the 'postcode' parameter with an example. The description adds value by specifying the output (prefecture, city, area), which the schema does not provide. This helps the agent understand what the tool returns.

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 the verb 'look up', the resource 'area information by Japanese postcode', and specifies the returned fields (prefecture, city, area). It is easily distinguishable from sibling tools (get_account_info, get_electricity_consumption) which serve entirely different domains.

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 usage context is implicitly clear due to the tool's specific domain (postal areas) versus siblings (account info, electricity consumption). It mentions 'No authentication required', indicating public availability. No explicit when-not-to-use guidance is needed given the narrow scope.

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