Upscale image

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

Annotations already establish readOnly=false and destructiveHint=false, so the description's job is to add context, which it does: it discloses that a new file is saved, the input is never overwritten, no new content is hallucinated, and runtime varies by hardware. That is meaningful behavioral detail beyond the annotations, though permissions/prerequisites are not addressed.

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 tight sentences, front-loaded with the core action and default, followed by model/timing context and output-safety guarantees. Every sentence carries information, though the model-name detail is the least essential.

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 output schema, the description usefully explains that a new file is written and where output_path constraints apply, and it covers the preview option's default-false behavior. Minor gaps remain around what the tool result returns when include_preview is false, but overall the definition is complete enough to call correctly.

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 every parameter is already documented in the schema, including the default-2 scale, the 8192 px maximum, and the never-overwrite output_path behavior. The description largely restates those facts, so it adds little beyond the structured fields; baseline 3 applies.

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 names a precise verb and resource ('Enlarge an image') and immediately bounds the operation with the default 2x factor and the 8192 px ceiling, so an agent knows exactly what the tool produces. Upscaling is inherently distinct from the sibling generate/edit/inpaint/outpaint tools, and the description reinforces this with 'adds no new content'.

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?

Usage is implied ('enlarge an image') and the model/timing context ('seconds on a PC GPU, longer on a Mac') helps set expectations, but there is no explicit when-to-use versus when-not, and no routing to or away from siblings like edit_image or inpaint_image. A minimum-viable level of guidance only.

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