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

With all annotation hints false, the description carries the full burden. It discloses the surgical nature (video track only, audio unchanged), the billing impact (~1/3 of full render), and the lip-sync risk warning. It doesn't discuss side effects like irreversible changes or error conditions, but the core behavioral traits are well-covered.

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 paragraph but every sentence adds distinct value: it leads with the core action and constraint, then provides usage context, billing note, and exclusion guidance. While slightly long, it is tightly packed and front-loads the critical 'VIDEO TRACK ONLY' caveat.

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 tool with no output schema and moderate complexity, the description covers the essential operational context: what it does, when to use it, constraints on the window (including speech), and cost implications. It doesn't state what a successful result looks like (since no output schema exists), but the side effects are clear enough for an agent to invoke it correctly.

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 descriptions cover all 6 parameters, so the baseline is 3. The description adds meaningful semantics: the window length constraint (1.5-8s), the purpose of `speechWindows` to avoid overlap with dialogue, and that `prompt` should match the master's style. These go beyond simple schema labels and help the agent construct valid calls.

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 states a specific verb ('re-render') and resource ('ONE time window of an existing rendered video') and explicitly limits scope to the video track, distinguishing it from a full re-render. It also gives a concrete use case ('the shot at 8 seconds glitches'), making the tool's purpose unambiguous even among many sibling video tools.

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?

It explicitly states when to use ('Use when one beat/shot is broken and a full re-render would waste...') and when not to ('Do NOT pick a window covering spoken dialogue'), and instructs to pass `speechWindows` to enforce the exclusion. This gives the agent clear decision criteria without needing to infer from context.

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