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

Annotations already flag destructiveHint=true and idempotentHint=true, but the description adds concrete value the annotations cannot: cancel discards the elapsed time entirely and is irreversible, plus an explicit instruction to confirm with the user before doing it. That is exactly the kind of consequence disclosure an agent needs before an irreversible call.

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?

Two compact sentences with the action list front-loaded and the destructive warning immediately after. Nothing is wasted, though the warning sentence is compressed to the point of slight terseness ('sans retour possible : demande confirmation avant').

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 2-parameter state-machine tool with no output schema, the definition covers the essentials: the action set, the irreversible branch, and the confirmation requirement. The only minor gap is that it does not state what happens to an already-paused timer on resume, which an agent may need to reason about.

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% and the action enum is already self-documented, so the schema carries the parameter burden. The description reinforces the meaning of 'cancel' (no time counted) but says nothing about 'pause' versus 'resume' semantics or the session_id parameter; 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 specific verbs and the resource ('la session de chrono en cours') and enumerates the three actions the enum supports, so the agent knows exactly what is being modified. It does not, however, distinguish this from the sibling tools dandori_start_timer and dandori_stop_timer, leaving a potential 'stop vs cancel' ambiguity unresolved.

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 useful operational guidance for one branch — that 'cancel' stops the timer without counting the time and cannot be undone, and that confirmation must be requested first. It offers no guidance on when to choose pause versus stop (a sibling tool) or on resume semantics, so selection guidance is only partially covered.

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