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

No annotations are provided, so the description carries the full behavioral burden. It discloses the important side effect that only one timer runs at a time and that starting a new one stops/saves the running one, returned as `stopped`. It also explains the rate fallback, though it does not describe the success return shape or any required permissions.

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 sentences, both essential. The core action is front-loaded, followed by the critical single-timer exception and the rate rule. There is no redundancy or filler.

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 7-parameter tool with no output schema and no annotations, the description is largely complete: it clarifies the timer lifecycle, entity association, rate fallback, and the stopped-timer return value. Minor gaps remain, such as whether contact/company/deal parameters are mutually exclusive and what exactly the started-timer response contains.

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 genuine value by explaining that the rate is taken from `rate` or falls back to the last rate used for the associated deal/contact/company, and by clarifying the optional entity association, which goes slightly beyond the schema's field 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 uses a specific verb ('Start') and resource ('the user's timer') and adds optional entity association to contact, company, or deal. The single-timer behavior further distinguishes it from sibling tools like time_timer_stop and time_log.

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 clearly conveys when to use the tool: to start a timer, optionally scoped to a deal/contact/company, with rate fallback behavior. It does not explicitly name time_timer_stop as the alternative for stopping without starting, but the sibling name and the one-timer rule make that boundary clear enough.

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