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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description nonetheless adds genuine behavioral context by disclosing the progressive tier structure and the applied rates (20.5%, 14.16%), which tells the agent how the computation is bracketed rather than just that it is a safe read.

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 purpose in one sentence, followed by the output key list and a single cross-reference. Every element earns its place, though the enumerated return keys overlap with the existing output schema and could be trimmed.

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 single-parameter calculator with an output schema, the description covers domain, jurisdiction, and calculation shape adequately; return values are additionally documented by the output schema. Only the absence of explicit sibling routing keeps it short of complete.

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?

There is exactly one parameter with 100% schema description coverage ('Annual net professional income in euros'), so the schema fully carries parameter meaning. The description adds nothing about the parameter itself, which matches the baseline 3 for high-coverage schemas.

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?

Specific verb + resource + jurisdiction: 'Calculate Belgian self-employed social contributions (cotisations INASTI)'. The scope is narrow enough (self-employed INASTI contributions) that an agent can immediately distinguish it from the many other Belgian finance siblings such as calculate_belgian_income_tax, calculate_belgian_salary, or calculate_belgian_pension.

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 qualifier 'self-employed' implies the population it applies to, but there is no explicit when-to-use or when-not guidance (e.g. salaried employees should use calculate_belgian_salary instead). The pointer to list_bundles is a discovery aid rather than usage guidance, so this remains implied rather than stated.

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