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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the safety profile is covered. The description adds genuinely non-obvious behavior: revision checking (optimistic concurrency) and, critically, that dryRun defaults to true so the call previews rather than writes unless overridden.

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 tight sentences with the core action front-loaded and no filler. Slightly under-specified rather than verbose, so brevity here is not purely a virtue.

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 an 11-required-parameter mutation with 9% schema coverage and only one described property, the description is too thin. It flags the critical dryRun default but omits expectedRevision mechanics, idempotency behavior and spec shape; the output schema removes the need to explain returns.

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 only 9% across 11 required parameters, so the description carries nearly the whole burden. It only gestures at timing ('explicit timing') and text/title concepts, leaving spec, itemId, idempotencyKey, expectedRevision and textKind semantics undocumented in both places.

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?

States a specific verb and resource ('Create or revise one title or text overlay with explicit timing') and scopes it away from audio and captions. It does not, however, differentiate itself from the sibling add_text_overlay, which an agent could easily confuse it with.

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?

Gives a useful when-to-use signal via 'dryRun previews by default' and a when-not via 'not spoken audio or captions.' But it names no alternative tool and gives no condition distinguishing it from add_text_overlay, leaving the primary routing decision to inference.

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