Add a transition

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

The description discloses important behavior beyond annotations: the result is shorter by exactly the overlap duration, and the second clip is conformed to the first's resolution and frame rate because xfade requires matching formats. Annotations (readOnlyHint=false, destructiveHint=false) are not contradicted; the description adds context about the non-obvious overlap and conforming behavior.

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 three short paragraphs, each earning its place: the first states the purpose, the second explains the critical overlap/conforming behavior, and the third lists transition options. It is front-loaded, free of fluff, and appropriately sized for the tool's complexity.

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?

Given the tool has 7 parameters, a nested EncodeOptions object, and an output schema, the description provides the essential operational semantics (overlap, conforming, transition choices). It does not cover crossfade_audio behavior or output_path defaults, but the schema and output schema fill most gaps. Overall, sufficiently complete for correct invocation.

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?

The schema already describes most parameters (71% coverage), including duration and transition options. The description adds conceptual meaning by explaining that clips overlap by 'duration' seconds and the result shortens accordingly, and it lists available transition families in plain language. This supplements the schema without repeating it verbatim, but it does not detail encode parameters or output_path behavior.

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 the exact action ('Join two clips with a cross-fade or wipe-style transition') with a specific verb and resource. It distinguishes the tool from sibling concat by focusing on transitions and overlap behavior, and enumerates the transition families (fade, wipe, slide, circleopen/circleclose).

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?

The description clearly explains the core usage: join two clips with a transition, with overlap duration and resolution/frame-rate conforming. However, it does not explicitly compare to alternatives like concat or trim, nor state when not to use this tool. The context is clear but lacks explicit exclusions or alternative recommendations.

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