Start a timer

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

The description discloses a critical behavioral trait: it stops an already running timer first. This goes beyond the annotations (readOnlyHint=false, destructiveHint=false) and is essential for the agent to anticipate side effects. This is a significant and well-communicated behavior.

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 two concise sentences. It front-loads the main action ('Starts the clock') and immediately adds the critical constraint. Every word earns its place with no redundancy.

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 the 10 optional parameters and no output schema, the description covers the most important behavioral context (auto-stop). It doesn't describe return values, but the tool is simple enough that this is acceptable. The schema handles parameter documentation, so the description is sufficiently complete.

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 does not add any parameter-level detail beyond what the schema already provides, but it doesn't need to since each parameter is well-described.

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 clearly states the tool's action with 'Starts the clock' and specifies the resource (a timer). It distinguishes from siblings by noting the one-running-timer-per-user constraint and the auto-stop behavior, making its purpose unambiguous.

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: it's for starting a timer, and it warns about the single-timer-per-user limitation. It doesn't explicitly mention alternatives like clockify_stop_timer or clockify_log_time, but the context is sufficient for most use cases.

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