Upscale Image

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

With no annotations, the description carries the full burden and does well: it discloses expected latency ('takes a few seconds') and the return shape (preview plus URL and id of the full-resolution PNG). It leaves unstated whether a new image is persisted or how it interacts with the source image, and no output schema exists to fall back on.

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 action and scaling choices, followed by the differentiator, latency, and return value. No filler or restated title.

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 two-parameter tool with no annotations and no output schema, the description covers purpose, latency, and return values, which is nearly everything an agent needs. The remaining gap is input-source behavior (id vs URL) and whether results are persisted or return-only.

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 enum for factor is already fully documented, so the description only echoes the 2x/4x choice. It adds nothing about the 'image' parameter, such as what happens when a stock/server id versus a remote http(s) URL is supplied.

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 ('Enlarge an image 2x or 4x') and names the underlying model (Real-ESRGAN). The clause 'Adds sharpness rather than new content' cleanly separates it from the sibling generate_image and edit_image, so an agent can route without opening a 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 a concrete use case ('prints and wallpapers') and a negative qualifier that rules out content-adding scenarios, which implicitly points at generate_image. It stops short of explicitly naming when not to use it (e.g., small inputs, non-photo assets) or naming alternatives by name.

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