Control playback

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

Annotations declare readOnlyHint=false and openWorldHint=false, so the safety profile is already carried by structured data and the mutating nature is consistent with the described actions. The description adds one genuinely non-obvious trait — `play` bypasses the user-gesture requirement — which is real value beyond annotations. It says nothing about failure modes (no video found, invalid ref), whether volume/mute changes persist, or the default targeting behaviour that the schema actually handles.

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, zero filler: the capability enumeration comes first and the one non-obvious caveat is front-loaded second. Nothing is repeated from the schema and nothing is wasted.

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?

With six parameters fully documented in-schema and no output schema, the description only needs to frame the operation set and any behavioural gotchas, which it does. The missing piece is a note on what happens when the target video is absent or the ref is stale, but that is a minor gap for a well-specified control 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 description coverage is 100% and every parameter is documented in-schema, including the action-to-parameter pairing (rate/time/volume) and the video ref default. The description adds no semantics beyond that, so the baseline of 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 names a concrete resource (a video) and enumerates every operation the enum supports: play, pause, seek, rate, mute/unmute, volume. That maps one-to-one onto the `action` enum, so an agent knows exactly what the tool does. It does not explicitly separate itself from near-neighbours like video_list or media_inspect, which keeps it 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?

There is no explicit statement of when to choose this over siblings or when not to use it; the only conditional guidance is the note that `play` works on pages requiring a user gesture, which implicitly tells the agent to reach for this tool rather than raw evaluate/click for playback. Usage is otherwise inferable from the action list alone.

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