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

With no annotations provided, the description carries the full burden. It clearly discloses the output unit behavior, the use of the 2026 scale, and the inclusion of the quotient familial cap. It does not describe potential error conditions or the exact response structure, but the most important behavioral nuances are present.

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 description is compact, front-loads the acronym and core concept, and then provides the essential unit distinction and legal sources. Every sentence adds value, with no filler or redundancy.

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?

The tool has no output schema and no annotations, so the description must explain the return format and calculation scope, which it does well. It states the percentage-point unit and the legal basis. It slightly under-specifies whether the result is a bare number or a structured value, but an agent can invoke the tool correctly with the schema.

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 the baseline is 3. The description does not add new meaning to the parameters themselves; it only clarifies the output unit and tax context. The schema already describes 'revenu_net_imposable' as household net income, and 'parts' and 'situation' are self-explanatory with their descriptions.

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?

The description clearly states the tool returns the household's marginal tax rate (TMI) under the 2026 French tax scale, including the quotient familial cap. It uses a specific verb ('Renvoie') and a specific resource, and it explicitly distinguishes itself from fiscal_prelevements_sociaux by unit, so an agent can tell them apart.

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 description gives an explicit when-not by naming the alternative fiscal_prelevements_sociaux and contrasting units: this tool returns percentage points (PERCENT), the other returns a fraction (RATE). It also implicitly states when to use it: whenever a marginal tax rate in percentage points is needed.

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