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

Despite annotations declaring destructiveHint=true and non-idempotent, the description adds substantial context the annotations cannot: partial-update semantics ('seuls les champs donnés changent'), that sans_fin=true removes the end condition, the one-message-per-day rule, closure/holiday skipping or shifting, quiet hours, the 60-day first-send window, and the mandatory preview-before-execute gate.

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 core action and the id provenance, then the mutation rule, then the confirmation protocol. The middle 'Règles :' run-on packs six constraints into one sentence, which is dense but each clause carries real operational information.

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 14-parameter destructive mutation with no output schema, the description covers partial-update behavior, scheduling constraints and the safe two-step confirm flow. It stops short of describing what the preview returns or how validation failures surface, which would be the remaining gap.

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, but the description adds cross-field meaning: sans_fin as the removal switch for either end date or send count, si_ferme=decaler shifting to the next open day, and the frequence↔jours / jour_mois / rang+jour_rang dependency. It still doesn't explain every parameter (e.g. heure bounds are only in the schema).

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 opens with a specific verb+resource: changing the text or rhythm of an existing recurring message, with the id sourced from lister_messages_recurrents. That clearly separates it from creation (programmer_message_recurrent) and lifecycle siblings (arreter/suspendre/reprendre), though it never names those alternatives explicitly.

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?

It gives an actionable usage protocol: call with confirmer=false to get a preview, show it to the person, then re-call with confirmer=true only after explicit agreement. What's missing is guidance on when to prefer this over programmer_message_recurrent or the suspend/stop siblings.

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