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

The tags [write, queued, priced] add important behavior beyond the annotations, indicating mutation, asynchronous processing, and cost. It also explains that worker_videos_replace produces the result and stores it as video_source, which is useful operational context.

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 dense but front-loaded with operational tags and the core purpose. The notation is compact, though the single-paragraph structure and internal shape reference make it slightly harder to scan.

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 complex tool with nested objects, no output schema, and 0% schema description coverage, the description covers the core replace payload and notes the return IDs. However, it leaves multiple parameters and the video_render_target structure undocumented.

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 0%, so the description must carry parameter meaning. It does well for video_replace, naming key fields, constraints like 1-3 READY characters, and provider enums, but omits several top-level parameters such as video_title, video_output, and video_keywords.

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 a specific verb and resource: creating a video by replacing people in a source video with picked characters. It distinguishes this from generic video-creation siblings by explaining the replacement mechanism and the worker_videos_replace pipeline.

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 use case is clear: use an existing storage video and substitute characters for people in it. It does not explicitly name alternatives like create_video or create_film_video, so it stops short of full routing guidance.

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