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

Goes well beyond the readOnly/idempotent annotations: discloses that 39 of 41 countries are modelled, that the Philippines and UAE keep only a statutory rate with a caveat and never a borrowed effective rate, and that every response leads with a disclaimer. This is exactly the kind of coverage/caveat context annotations cannot carry.

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, leading with what the tool computes and the gap. Every sentence carries information, though the disclaimer and 41-country caveat sentences make it heavier than strictly needed.

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?

An output schema exists, so return values need not be explained. Combined with annotation safety profile and the disclosed country coverage caveats, an agent has everything required to call this correctly.

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?

Adds meaning beyond the 80%-covered schema: `metric` selects the ranking metric with eatr as default, `sort=highest` overrides the lowest-first default, and the country/countries/neither interaction defines when each param applies. Marginal gains only, since the schema already documents most parameters.

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: forward-looking effective average/marginal tax rate and cost of capital beside the statutory rate, with the gap. It clearly distinguishes itself from siblings like compare_tax_rates, compare_tax_burden and withholding_tax by naming the OECD EATR/EMTR methodology.

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?

Explains the three usage modes explicitly: `country` for one, `countries` for a side-by-side, neither for a ranked list, plus metric and sort defaults. It does not name alternative sibling tools, but the routing within the tool is fully specified.

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