tv_video_state

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

With no annotations, the description carries the full burden of disclosure. It explains the sampling behavior (two samples to determine if currentTime is advancing) and lists the return fields. It does not mention prerequisites (e.g., a video element must exist) or failure modes, but covers the core behavior well.

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 a single, front-loaded sentence that packs all essential information without waste. Every phrase contributes: the resource, the output fields, and the use case.

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 there is no output schema, the description compensates by listing the return fields. It also explains the two-sample methodology. It lacks a bit of detail on return value structure or edge cases, but for a simple snapshot tool with 2 optional params, it is largely 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 description coverage is 100%, so the baseline is 3. The description mentions 'two samples' which relates to sampleGapMs, but does not add meaningful detail beyond what the schema already provides for device and sampleGapMs.

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 uses a specific verb ('snapshot') and resource ('<video>') and clearly lists the exact fields returned (currentTime advancing, readyState, size, muted, src, MediaError code). It distinguishes itself from sibling tools like tv_screenshot by positioning itself as the reliable way to confirm playback when a screenshot would be black.

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 a clear use case: confirming playback when a screenshot would be black. This implies when to use it over tv_screenshot, though it does not explicitly name alternatives or state when not to use it. The guidance is present but not exhaustive.

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