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

Annotations already flag destructiveHint=true and idempotentHint=false, and the description adds real context beyond them: cancel is explicitly irreversible ('sans retour possible') and the timer is screenless/no-display. It still omits whether complete produces a summary or whether permissions/plan limits apply.

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 compact sentence that front-loads the primary action, then immediately branches to the two terminal actions with their key caveat. Zero redundant wording.

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 stateful, destructive three-action tool with no output schema, the description covers the lifecycle but says nothing about return values, failure modes (unknown ID, session already active), or defaults for duration_minutes and break_minutes. Adequate but with clear gaps.

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?

With 80% schema coverage and per-field descriptions that already say which parameters apply to start versus complete/cancel, the schema does the heavy lifting. The description only reinforces the action names and adds no format, default, or constraint detail beyond them.

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 the exact resource (a focus session, described as a screenless timer) and enumerates the lifecycle verbs start/complete/cancel, so the agent knows precisely what the tool handles. It does not differentiate from a likely overlapping sibling such as dandori_control_timer, which keeps it from a 5.

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 implies the intended flow (start first, then either complete or cancel) and that cancel is the abandonment path, which is genuine guidance. However, it never states when to prefer this over the timer-control sibling, nor what happens if a session is already running or an ID is invalid.

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