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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile is covered. The description adds real behavioral context beyond that: the hard cap of four conditions, the grouping units (里/鄉鎮), and the fact that results are counts plus aggregated population rather than raw rows.

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?

Front-loaded with the core capability and returns in two sentences, with the example placed where it clarifies rather than pads. Slightly diluted by restating the same content in Chinese and English, but no genuinely wasted text.

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?

With no output schema, the description carries the return-value burden and does describe the shape (matching cell count, population, aggregated by 里/鄉鎮). For a four-parameter filtering tool this is nearly sufficient; only the alternative-tool routing is missing.

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 100%, so the schema already documents top, town, unit, and the nested condition fields (metric, op, value) with enum meanings. The description reinforces the 'max four conditions' constraint but adds no syntax or semantics the schema lacks — baseline 3.

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?

Names a specific action and resource: find 125m grid cells satisfying up to four conditions, and states what is returned (cell count, population) and how it is aggregated (by 里/鄉鎮). The worked example ('離公車站超過 500 公尺、又住超過 100 人') makes the scope unambiguous, though it does not explicitly name the sibling it differs from (e.g. rank).

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 example implies a use case (multi-criteria filtering), but there is no explicit statement of when to use this versus rank, need_ranking, or compare_groups, nor any when-not guidance. Usage is inferable rather than stated.

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