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

With destructiveHint: true already provided, the description adds valuable behavioral context: 'Seuls les champs fournis sont modifiés' (only provided fields are modified) and clarifies the amount unit in euros. This goes beyond the annotation without contradicting it.

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 two concise sentences, front-loads the primary action, and contains zero filler. Every word adds value, making it an exemplar of brevity.

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?

Given the 12-parameter schema, absence of an output schema, and only a destructiveHint annotation, the description is too thin. It fails to mention error handling, return values, permission requirements, or field-specific constraints, leaving significant gaps for an agent to invoke 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?

Schema description coverage is 0%, so the description must compensate. It only clarifies the 'amount' unit (euros) and the partial-update behavior affecting all fields. The remaining 11 parameters (e.g., tva_rate, tourist_tax, platform_fee) are left entirely to their self-explanatory names, which may not be sufficient.

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's action and target: 'Met à jour un revenu locatif existant' (updates an existing rental income). This specific verb+resource pairing distinguishes it from sibling tools like create_income, delete_income, and update_expense.

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 implies usage context ('existing' income, partial update) but does not explicitly state when to use this tool versus alternatives or provide exclusions. It lacks the explicit alternative naming seen in high-quality examples, so it remains at the implied level.

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