addCameraFullscreen

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

Annotations only give the generic safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=false); the description adds real behavioral detail the annotations cannot: a precondition on asset camera tracks and a refusal-rather-than-partial-write failure mode. That is exactly the extra context the annotations leave uncovered.

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?

Three sentences, front-loaded with the action and span, followed by the precondition and the failure behavior. No filler or restatement of the name.

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 three-parameter mutation with no output schema, the description covers the action, the span semantics, the required precondition lookup, and the refusal behavior. An agent has everything needed to call it correctly or explain why it cannot.

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 coverage is only 33%, so the description must carry weight; it does by clarifying that startSec/endSec are virtual seconds bounding the region and that the span must map to non-empty camera footage, which is a semantic constraint absent from the bare numeric minimum:0 schema. projectId semantics live in the schema, so nothing further is needed there.

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 (add) plus resource (camera-fullscreen region) and scopes it to a span of the edited timeline in virtual seconds, with the rendered effect made explicit ('webcam fills the frame'). An agent can distinguish it from generic effect tools, though it never names its closest sibling setCameraFullscreen, so no explicit sibling differentiation.

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?

Explicitly directs the agent to check assets[].hasCameraTrack (or hasAnyCamera) via getCurrentDocument first, and states the when-not case: it does nothing on footage lacking a camera track. It even prescribes the response to refusal ('say so instead of retrying'), which is unusually complete routing.

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