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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses the API-key requirement per country, the country_not_available and key_required failure modes, the null fields for Tunisia, and the 'reading of public texts, not tax advice' disclaimer. That is meaningful behavioral context an agent could not infer from the structured fields.

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 purpose is front-loaded in the first clause, but the rest is a single sprawling run-on sentence with deeply nested parentheses about Algeria and Morocco that is hard to parse. Detail is disproportionate to the simple two-parameter read operation.

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?

There is no output schema, so the description carries the burden of describing return contents, and it does enumerate the returned rate categories, the per-entry legal article, effective date and source page. It is dense but covers what an agent needs for this lookup; only the exact response shape remains unspecified.

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 both lang and country are already fully documented in the schema, including defaults, the ISO alpha-2 pattern, and the error behavior. The description adds no new parameter syntax or format detail beyond what the schema provides, so the baseline 3 applies.

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 ('Get the business tax rates in force in 2026 for a country') and enumerates the exact contents returned (corporate income tax, VAT, withholding, plus country-specific personal_income_tax and flat_tax). An agent can distinguish this from siblings like get_vat_regimes or get_social_contributions without opening the 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 real operational context: DZ is the default, only DZ answers without an API key, TN and MA return key_required, and list_countries shows which countries/datasets are live. It also points to calculate_ifu for IFU eligibility. It stops short of an explicit 'use this instead of X when Y' routing statement against the tax siblings.

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