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

Annotations already declare readOnlyHint=true and idempotentHint=true, covering safety. The description adds context beyond those: the result is ESTIMÉ based on yield/revaluation/rate hypotheses and interest+insurance are deductibleches. It also names the financial method (tableau d'amortissement, TRI de flux), which helps the agent understand the calculation nature without contradicting the annotations.

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?

Three compact sentences: the first states the purpose and outputs, the second adds the critical estimation caveat, the third routes to sibling tools and cites sources. No fluff or redundancy; every sentence earns its place and is front-loaded.

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 description is complete for an 8-parameter calculator: it names expected outputs (mensualité, effort d'épargne, fonds propres, TRI) even without an output schema, states the estimation nature, and gives usage alternatives. The only minor gap is not explaining what 'fonds propres' or 'effort d'épargne' mean, but that is domain vocabulary an agent would infer from the schema and context.

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% (all 8 parameters have descriptions), so the schema already carries full parametric meaning. The description does not add extra semantics about parameter syntax or relationships; it mentions deductible interest and TRI but does not link them to specific fields. Baseline 3 is appropriate.

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 states a specific action ('Projette une SCPI financée à crédit') and lists concrete outputs (mensualité, effort d'épargne, fonds propres, TRI). It distinguishes itself from sibling tools by explicitly naming the cash-purchase and démembrement alternatives, so an agent can tell them apart without opening their schemas.

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 explicit conditional routing: 'Achat au comptant → simulateurs_scpi; nue-propriété ou usufruit → simulateurs_demembrement_scpi.' This is a clear when-to-use vs. when-not-to instruction naming exact alternatives, leaving nothing to inference.

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