Start a timer

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

Beyond the annotations (readOnlyHint=false, destructiveHint=false), the description discloses that any other running timer is stopped automatically, a meaningful side effect. It also notes the scope ('for today') and authentication requirement, adding useful context without contradicting the annotations.

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: the first states the action and scope, the second provides the side effect and a prerequisite. It is front-loaded and contains 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?

For a simple timer tool, the description covers the main behavior, a critical side effect, and a prerequisite for one parameter. It does not discuss error conditions or return values, but given the absence of an output schema and the presence of annotations, this is acceptable.

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 description coverage is only 33% (only 'notes' has a description). The description adds semantic value by indicating that task_id should be obtained from list_project_tasks, but it does not explain project_id beyond the name. It partially compensates for the low schema coverage but leaves a gap.

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 action ('Start a running timer'), the resource ('a project + task for today'), and the authentication context ('authenticated user'). It distinguishes from siblings like stop_timer and log_time by specifying 'running 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 provides clear usage context: it is for the authenticated user's timer for today, and it explicitly mentions that any other running timer is stopped. It also directs users to list_project_tasks to obtain task_id, which is a helpful prerequisite. However, it does not explicitly differentiate from log_time (manual entry) as an alternative.

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