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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description's only added behavioral information is that the call is free, which is useful but not about side effects, repeat-save behavior, or limits. It neither contradicts nor enriches the annotation picture much.

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 core is front-loaded and efficient, but the closing 'Free. Cost: Free: no credits.' is a redundant duplicate of the same fact stated twice in one breath. That waste undercuts an otherwise tight three-sentence definition.

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?

An output schema exists, so return values need not be explained, and the description supplies the missing piece — where output_id comes from and where asset_id goes. The naming mismatch between the input 'output_id' and the resulting 'asset_id' is introduced without explicit reconciliation, which is the only real gap.

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 both video_id and output_id are already documented in the schema, including the example 'short-2-9x16'. The description reinforces the source of output_id but adds no format or edge-case meaning beyond what the schema states — 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 first sentence names a specific verb ('keep') and resource ('a finished clip (or hook, or film) of a video') and explains what the result becomes — a reusable asset. It does not distinguish itself from sibling list_assets or import_asset, so an agent must infer the difference between saving a rendered clip and importing an external asset.

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 concrete guidance: read output_id from check_video first, then use the resulting asset_id in edit_video or create_video. That is clear 'use it like this' instruction. It stops short of stating when NOT to use it versus import_asset or list_assets, so no exclusions are offered.

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