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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety and scope are covered externally. The description adds the useful edge-case detail that large offices with dedicated postcodes are included, but it says nothing about whether multiple addresses can come back for one postcode or what an empty result looks like.

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?

One compact sentence with the essential constraint front-loaded and no filler. It is appropriately sized for a single-parameter lookup, though the trailing 'including large offices' clause slightly buries the key scope statement.

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, non-destructive lookup with full annotation coverage and no output schema, nearly everything an agent needs is present. The only meaningful omission is whether the result can be a set of addresses rather than a single one, which matters for handling the response.

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 single parameter is fully documented in the schema (7 digits, hyphen optional, example 530-0001), so the schema carries the weight. The description only restates the 7-digit requirement and adds no format or validation detail beyond it, which is the baseline expected at 100% coverage.

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 gives a specific verb and resource ('Get the address for a 7-digit Japanese postcode') and narrows scope by country and format, so an agent can tell it apart from a fuzzy tool like search_address. It stops short of naming any sibling explicitly, so it is clear but not fully differentiated.

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 Japanese postcode' constraint signals this is for exact postcode input rather than free-text address search. There is no explicit when-to-use or when-not-to-use statement, and no mention of what to do with invalid or partial postcodes.

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