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

Beyond the annotations, the description discloses that the tool drives a real browser, takes ~15-30s, returns a job_id to poll with check_job after ~35s, and produces clean errors for unsupported or plan-limited cases. It also states the return shape, which is essential since there is no output schema. Nothing contradicts the annotations.

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 information is front-loaded and each paragraph addresses a distinct operational concern: purpose, account semantics, resolution constraints, timing, and return format. Some UI-context detail like the "Download panel" and "1K/2K/4K picker" could be trimmed, so it is not maximally concise.

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?

Given the lack of an output schema and no parameter descriptions, the description covers input semantics, expected output fields, polling behavior, error handling, and account prerequisites. No material detail an agent needs to invoke the tool correctly is missing.

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 property descriptions are absent (0% coverage), but the description fully compensates by explaining account ownership, the source of media_id, and the target_resolution enum with its failure modes. An agent can correctly populate every parameter using only this description plus the schema's required/default flags.

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 opens with a specific verb and object: "Upscale an existing generated image... to a higher resolution", explicitly scoped to output from a prior generate_image call. This clearly distinguishes it from sibling tools like upscale_video or fetch_media 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?

It provides strong contextual guidance: the account must own the media_id, media_id comes from generate_image, and unsupported 4K cases should be reported rather than retried. However, it does not explicitly contrast alternatives (e.g., upscale_video) or give a when-not-to-use statement, so it falls just short of a 5.

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