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

Annotations declare only the write/safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=false); the description adds genuinely new behavioral context: the operation is free, it returns the video id, and the returned player card self-checks so the agent should not poll get_video. That last point is non-obvious operational guidance not available in any structured field.

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?

It is front-loaded with the core action and the output, then branches into sources; the one-word 'Free.' and the card/polling note both earn their place. It runs as a dense multi-clause block rather than cleanly separated statements, which slightly hurts scannability but not substance.

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 8-parameter mutation tool with nested file objects, it covers prerequisites, source selection, optionality, and return value (the output schema handles the rest), so most of the burden is met. However, it omits any differentiation from the sibling 'make_videos', which is the most consequential omission for correct tool selection in this suite.

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%, so the baseline is 3, but the description goes beyond the schema by grouping the eight parameters into a decision structure the schema presents only piecemeal: app footage is 'one of' four alternatives or nothing, and music mirrors those sources and is optional. That mutual-exclusion/branching logic is the main value added.

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?

It states a precise verb and output: it burns a hook line and app footage onto a completed clip to produce a finished vertical UGC video, and it names the required prerequisite (a completed clip). The one gap is that it never distinguishes itself from the near-identical sibling 'make_videos', which an agent could easily confuse with this singular tool.

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 gives real routing guidance: the clip must already be completed (get_video), leaving 'clip' empty selects the user's newest clip with no need to list first, and it enumerates the four mutually exclusive app-footage sources (recording_file, recording_upload, app_video_url, or on-file from first_videos). It also explicitly says not to poll get_video while the result card is showing. It stops short of stating when to prefer this tool over make_videos.

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