create_split_screen

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

No annotations are provided, so the description carries the full burden, yet it omits the operationally important traits: whether an existing file at outputPath is overwritten, how mismatched clip durations or resolutions are handled, and roughly how long/reliably a two-input encode completes. It does disclose the composition model (stacked vs side-by-side, audio mixing, subtitle embedding), which is why it is not a 1.

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 sentences with zero filler: the core action and output framing come first, capability details second. Nothing is repeated and every clause carries information.

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 7-parameter, file-writing tool with no annotations and no output schema, the description is adequate on composition but silent on the return value (does it yield the output path or nothing?), overwrite behavior, and failure modes. An agent could call it correctly but not predict its side effects.

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 100% and every parameter, including both enums and their defaults, is already documented in the schema. The description restates the layout and audio behavior in prose but adds no new constraints, formats, or edge cases, so the baseline 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 gives a specific verb and resource — 'Combine two video files into a split-screen video' — plus the spatial arrangement options, which clearly separates it from a plain concat_media call. It never names a sibling or states the boundary explicitly, so an agent must infer the distinction from the tool name alone.

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?

Usage is only implied via the mention of Reels/TikTok and the layout options; there is no statement of when to pick this over concat_media, add_overlay, or reformat_aspect_ratio, and no prerequisites (e.g., matching durations, codec compatibility) are called out.

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