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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is known; the description adds the missing detail that what gets destroyed is your label, plus the unusual 'Cost: Free' signal. It says nothing about what happens to unfinished edits or whether the returned link is permanent, but with annotations covering the core behavior this is solid added context.

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?

A single sentence ordered well: trigger first, effects second, cost last. Every clause carries information an agent needs before calling.

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 the returned link need not be explained, and the description flags that a link comes back. For a one-parameter, idempotent termination call this is nearly complete; only the interaction with an unfinished session is unstated.

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 the single video_id parameter already documents its default ('the open one if left out'). The description adds no parameter-level meaning at all, 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 specific action and its concrete effects: it 'clears your label' and 'gives the link to end with'. That is more than a restatement of the name and clearly marks this as the session-termination call, though it never explicitly names its counterpart (start_video) the way a 5 would.

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?

'Call when done changing a video' gives a clear, actionable trigger condition, and 'Cost: Free' reinforces that calling it unnecessarily is cheap. There are no explicit when-not conditions or named alternatives, which keeps it short of a 5.

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