upscale_image

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

No annotations, so the description carries the burden. It discloses the default model and the cost-free nature of estimate_only indirectly, but never states what a normal invocation returns (a URL? an image?), whether the real run is charged, or any latency/rate limit.

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 short sentences, front-loaded with the core action and constraint before the model default and link requirement. Nothing is wasted.

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?

With no annotations and no output schema, the description should explain what comes back from an upscale call; it does not. It is adequate for invoking the tool but leaves the agent guessing about the return shape and cost implications of a real run.

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 documents model, prompt, image_url and estimate_only. The description adds only the model default and the provenance hint for image_url, which is a marginal gain over the schema.

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+resource (sharpen and enlarge an image) and, crucially, the scope constraint 'without changing what is in it', which separates it from edit_image and generate_image without opening any 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?

Gives practical context (default model applies unless you name another; image_url must be an https link and 'links returned by this server work'), but never states when to choose this over upscale_video, edit_image, or generate_image.

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