app_time_summary_tool

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

With no annotations present, the description carries the full burden, but it does disclose meaningful behavioral traits: the values are approximate and gaps are capped at 5 minutes. It omits any auth/permission requirements or how the capped gaps affect interpretation, keeping it at a minimum-viable 3.

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 short sentences, front-loaded with the purpose followed by parameter format notes; no filler. Slightly terse on the parameter side, but appropriately sized.

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?

An output schema exists, so return values need no explanation, and the approximation caveat is covered. Still missing is guidance on when to use it versus siblings and any permission/scope context for a 2-param analytic tool.

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 0%, so the description must compensate, and it does document the accepted formats (epoch or YYYY-MM-DD) for both params. However, it doesn't clarify that end is optional/empty by default or how the window boundaries are treated, leaving a partial 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?

States a specific computation (per-app foreground time) and the method (event gaps in a window), which is enough for an agent to distinguish it from search_events or activity_coverage_tool. It does not explicitly name or contrast a sibling, so it stops short of a 5.

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 never says when to prefer this over alternatives like activity_coverage_tool or search_events, nor does it state any prerequisite conditions. Usage is only implied by the resource computed.

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