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

No annotations, so the description carries the full behavioral burden. It does disclose two real traits — a hard 50-item batch ceiling and, via "PRO.", a paid/subscriber gate — but says nothing about read-only semantics, partial-failure behavior for invalid postcodes, rate limits, or the shape of results.

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?

Extremely compact and front-loaded, with the pro-tier marker first and the constraint second. Nothing is wasted, though the terseness borders on under-specification rather than deliberate concision.

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 no annotations and no output schema, the description should explain at least what a resolution returns and how failures are surfaced. Neither is present, and the sibling relationship that would orient an agent is left entirely implicit.

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 50%: access_token is documented in-schema, while the postcodes array has only a type. The description partially compensates by supplying the critical max-size constraint (50) on that undocumented parameter, but adds nothing about format (7-digit? hyphenated? with/without 〒).

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?

"Resolve up to 50 Japanese postcodes" gives a verb and a resource, plus a useful scope limit, but "resolve" is vague — it never says what a postcode resolves into (addresses? regions?). It also fails to differentiate from the sibling postal_lookup, which presumably does the same thing for one postcode.

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?

No when-to-use guidance and no mention of the sibling tools. An agent cannot tell from this text why it should pick batch_postal over postal_lookup or all_matches, or what happens if the input exceeds 50 items.

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