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

Annotations already cover the safety profile (readOnly, non-destructive), and the description adds real behavioral context beyond them: the output video is surfaced as a resource link when available, and Character Swap projects include replayable settings (r2Keys, keepOriginalVisualRanges, resolution, sceneMatch, saveAudio) plus signed previews. This is meaningful disclosure an annotation cannot carry.

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?

Front-loaded with the core action and return set, then layers the Character Swap special case. Two dense sentences with no wasted filler, though the second sentence is somewhat long.

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?

There is no output schema, so the description appropriately enumerates the return payload (status, outputUrl, brief, per-format asset tiles) and the Character Swap extension. An agent knows what it will get back and how the resource link behaves.

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 description coverage is 100% and the single videoId param is already documented as a 'Project UUID from list_videos'. The description restates 'by its id' but adds no format, sourcing, or edge-case detail beyond the schema, 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?

States a specific verb and resource ('Fetch one video project by its id') and enumerates what is returned, which distinguishes it cleanly from the sibling list_videos. An agent can tell this is the singular retrieval counterpart to the list operation without opening the schema.

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 implied (fetch a single project by an id obtained from list_videos, per the schema text), and the Character Swap note hints at a replay workflow, but there is no explicit when-to-use/when-not guidance or comparison against alternatives such as get_job.

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