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

Beyond the read-only/idempotent annotations, it discloses the coverage gap (22 of 41 spine countries) and that missing countries return NO_DATA naming the gap rather than a modelled figure. It also flags that responses carry a 'for information only' disclaimer, which is non-obvious behavioral context an agent must relay.

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?

Dense but front-loaded, with scope stated before caveats and parameter mechanics. The long parenthetical and run-on clauses make it heavier than necessary, though nearly every clause carries information.

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 6-param tool with an output schema, the description covers scope, coverage limitations, default ranking behavior, and the informational disclaimer. Return-value description is correctly delegated to the output schema, leaving only minor parameter details unaddressed.

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?

With schema coverage at 50%, the description compensates by explaining the interaction the schema cannot: that omitting `country`/`countries` triggers a ranking, ordered cheapest first by `household` and `unit` with their defaults. It adds little on `limit`, but the enum parameters are well covered.

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+resource (net full-time centre-based childcare cost after benefits and tax, from the OECD tax-benefit model) with the exact household scenarios modelled. The scope is precise enough to separate it from siblings like compare_total_cost and compare_food_cost without opening any schema.

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?

Gives clear routing for `country` (one) vs `countries` (side-by-side) vs neither (ranking), plus sort direction and the OECD-membership limitation. It never names a sibling alternative or an explicit when-not-to-use condition, so it falls short of a 5.

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