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

Beyond the read-only/idempotent annotations, the description discloses substantial behavioral caveats: per-metric year coverage (population 97–114, crashes 111–114, income 111→112, turnout by election cycle), the fact that 97–106 covers only certain counties, that pre-establishment figures for new neighbourhoods are estimates and excluded from comparison, that boundary-adjusted neighbourhoods are skipped with reasons listed, and that the tool reports magnitudes without causal claims.

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 core operation is front-loaded and every clause carries a constraint (year ranges, exclusions, threshold units), so little is filler. It is dense and parenthesis-heavy, which slows reading, but the length is justified by the number of metrics and caveats.

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 six-parameter comparison tool with no output schema, the description covers metric scope, data coverage limits, threshold semantics, and exclusion rules well. It does not describe the shape of the result beyond 'top increases/decreases,' leaving result interpretation mildly underspecified.

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 100%, so baseline is 3, but the description adds real value: it explains the default threshold values per metric (population 500, crash 5/20, income 5, turnout 3), states the unit of the threshold (people/cases/10k NT$/percentage points), and describes the valid year ranges per topic that constrain from/to.

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 and resource: compare two years and rank neighbourhoods by largest increase/decrease across population, crashes, income, and turnout. It names the reference implementation ('跟網站 07「看變化」同一套') and lists the exact metrics compared. It does not, however, distinguish itself from the sibling compare_groups, which an agent could easily confuse with it.

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 context is implied by the metric list and the note that thresholds are user-supplied, so an agent can infer this is for two-period difference ranking. But there is no explicit when-to-use versus compare_groups, rank, or need_ranking, and no statement of exclusions relative to those siblings.

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