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

Annotations provide readOnlyHint=false and openWorldHint=true, but the description adds critical behavioral context: the tool is asynchronous (returns a generation_id rather than the upscaled video), it has a 10-second duration limit, and it costs $0.80 per video. This is exactly the kind of behavioral disclosure that helps an agent avoid hanging or misinterpreting the response. It doesn't mention failure modes or rate limits, but the key async behavior is well covered.

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?

Three sentences, each earning its place: the first states the core action and output resolution, the second gives pricing and limits, the third explains the async workflow. The most important operational detail (async behavior) is front-loaded in the final sentence, and there is zero filler.

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 single-parameter tool with a 100% documented schema, the description covers the essential operational context: what it does, what it costs, what the limits are, and how to retrieve the result. The only gap is that it doesn't describe the output format of get_generation or what the final result looks like, but since there's no output schema and the async pattern is clearly explained, this is a minor omission.

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%, so the schema already fully documents the single 'video' parameter. The description adds context about the video constraints (up to 10s, 1080p) which is useful, but doesn't add new parameter-level semantics beyond what the schema provides. Baseline 3 is appropriate.

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 ('Upscale'), a specific resource ('videos'), and a concrete target resolution ('to 1080p'). It also includes pricing and duration limits, which further disambiguate it from siblings like ai_video_colorizer, ai_video_restyle, and upscale_image. The tool's identity is unmistakable.

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 description clearly explains the asynchronous workflow: it returns a generation_id and instructs the agent to call get_generation until status is 'completed'. This is explicit usage guidance for the primary flow. However, it doesn't explicitly state when NOT to use this tool versus alternatives like upscale_image or ai_video_restyle, though the name and purpose make the distinction fairly obvious.

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