probe_asset_duration

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

No annotations are provided, so the description carries full responsibility. It discloses the memory side effect ('remember it'), the non-download behavior ('reads the header of the copy we already hold, no download, no third-party CDN'), and the sentinel null semantics ('UNMEASURED, never zero'). This is significantly more transparent than typical minimal descriptions.

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 three sentences, front-loads the core purpose, and each sentence earns its place: measurement action, operation mechanism, null meaning, and use context. There is no filler or redundant restating of the tool name.

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 one-parameter tool with no output schema and no annotations, the description is unusually complete. It tells the agent what is measured, how it is done, what is not done (no download/CDN), what is returned, what null means, what side effect occurs, and when to apply it.

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?

With only one parameter and 100% schema description coverage, the schema already explains asset_id as 'The watch asset id of the public ad to measure.' The description reinforces that the ad must be PUBLIC but does not add new meaning to the parameter beyond what the schema provides, so baseline 3 applies.

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 opens with a specific verb and resource: 'Measure how long a PUBLIC ad's creative actually runs, in seconds, and remember it.' It also names the return shape ({duration_seconds}) and clarifies the measurement scope. This distinguishes it from sibling tools that center on performance, comparison, or deconstruction.

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 gives explicit timing guidance: 'Use before acting on an ad's length when the corpus says its duration is unknown.' It also scopes the tool to PUBLIC ads and explains exceptional cases through null. It does not explicitly name a fallback or alternative tool, so it stops just short of the strongest when/when-not/alternatives guidance.

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