Start the timer

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

Beyond the annotations, the description discloses critical behavior: the timer is shared, only one can run, an already-running timer returns TIMER_ALREADY_RUNNING with details, and takeOver discards the running session with elapsed time lost and no time entry written. This gives the agent the safety-critical context needed for correct invocation. No contradiction with annotations; destructiveHint=false reflects the default non-destructive path.

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?

The description is front-loaded with the core action and uses a compact paragraph. It is somewhat dense, but each sentence adds necessary operational or safety information, so the length is justified.

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?

Given that there is no output schema and six optional parameters, the description covers the most important operational facts: single-timer constraint, conflict response, destructive takeOver semantics, and goal linking. It does not describe the success return payload, but this is a minor gap for a start action whose parameters are already well documented in the schema.

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. The description adds meaningful parameter guidance by warning that takeOver is destructive and by directing the agent to attach goalId when work belongs to a goal so stopping the timer credits that goal. This goes beyond the schema descriptions.

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 and resource: 'Starts the shared GoalSlot timer for this account.' It also clarifies this is the same timer seen in web/mobile apps, not a private one, and contrasts clearly with the sibling stop_timer tool by describing start behavior.

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 provides clear context: start the timer when work begins, and because only one timer can run at a time, do not use takeOver autonomously. It instructs the agent to surface the existing session and let the user choose to stop or replace it, effectively routing toward goalslot_stop_timer, though not by name.

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