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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real domain behavior beyond that: the schedule is indicative only, assumes a fixed rate, excludes insurance and fees, and the final payment is adjusted for rounding. It does not describe how rounding is applied or how the periods are laid out.

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?

A single dense sentence with no filler: the output, the rate assumption, the exclusions and the last-payment adjustment are all front-loaded. Nothing could be removed without losing a constraint.

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?

With no output schema, the description must carry the return-value burden, and it does so only at a high level (monthly schedule, adjusted final payment). It omits the per-period breakdown (principal vs interest split), currency of the output, and the fact that a 30-year/20% cap applies. Adequate for a simple read-only calculator, but not fully self-contained.

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 each parameter (principal in euros to the cent, annual nominal rate not TAEG, integer duration) is already documented in the schema. The description adds only the fixed-rate assumption and confirms that insurance and fees are outside the calculation; it contributes no per-parameter meaning, 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?

The description names a specific verb and output ("Produit un échéancier indicatif mensuel") plus the calculation mode ("à taux fixe") and explicit scope exclusions ("hors assurance et frais"). It is clearly distinct from a single-payment calculator, but it never names or contrasts with the sibling calculate_monthly_payment, leaving the differentiation implicit.

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?

Usage is only implied: the word "échéancier" suggests this is for full schedule generation rather than one payment, and "indicatif" signals a non-binding estimate. There is no explicit statement of when to prefer this over calculate_monthly_payment, and no prerequisites or exclusions beyond the fee/insurance caveat.

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