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

No annotations exist, so the description carries the full burden. 'FREE' usefully signals no cost/auth barrier and the return fields are named, but nothing is said about invalid/unknown postcodes, accepted input formatting (hyphen or not), or error behavior for a lookup that can clearly fail.

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?

Two short fragments, front-loaded cost note then the core action — nothing wasted. It is perhaps over-terse for the amount of input-format ambiguity the tool has.

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 one-parameter, no-annotation, no-output-schema lookup, naming the returned fields is the main thing needed and it is present. Missing input-format and failure-mode guidance leaves the definition adequate but not complete.

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 0% and the single string parameter is undocumented in the schema, but the description compensates partially by specifying the value must be a 7-digit Japanese postcode. It stops short of stating whether hyphens or spaces are tolerated, or whether leading zeros matter.

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?

States a specific verb (Resolve) and resource (7-digit Japanese postcode), plus the shape of the result (prefecture/city/town). An agent can tell this is a single-postcode geocoder, though it never names the sibling batch_postal to contrast the single vs batch split.

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?

Usage is only implied — the '7-digit' singular framing suggests one postcode at a time and siblings like batch_postal/all_matches hint at alternatives, but the description never says when to use this instead of them or what those tools do.

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