start_timer

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

The description goes beyond annotations by clearly stating the non-obvious side effect of stopping any other running timer. This is critical for an agent to understand the tool's behavior, especially since annotations only indicate it's not read-only.

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 extremely concise with two sentences that front-load the essential purpose and key behavioral constraint. No unnecessary words.

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 tool's simplicity (3 parameters, 1 required, no output schema), the description covers the core behavior and side effects. It could mention error handling or prerequisites, but overall it 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?

The input schema already has 100% coverage with detailed descriptions for each parameter. The tool description does not add additional semantic information beyond what is in the schema, so a baseline score of 3 is appropriate.

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 explicitly states 'Start a timer on a project' and notes it stops any other running timer, clearly distinguishing it from sibling tools like stop_timer or get_active_timer.

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 explains that it stops any other running timer because only one active timer is allowed, providing clear context for when to use. It does not explicitly list alternatives or when not to use, but the behavior is adequately explained.

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