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

Annotations already cover the safety profile (readOnlyHint=false, destructiveHint=false), and the description adds the return behavior ('Returns a link to the upscaled image'). However, it does not mention any processing time, credit cost, or side effects of upscaling, so the behavioral context beyond annotations is thin.

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?

Two sentences, no redundancy, and the core action is front-loaded before the output statement. Every word earns its place.

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 simple two-parameter tool, the description plus schema is nearly sufficient: inputs are explained, factor defaults are in schema, and the output link is stated. It only lacks a brief note about scope/limits (e.g. maximum source image size or credit consumption), so it is complete enough but not exhaustive.

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%: both imageUrl and factor are documented, including the default factor and the required fal-upload-source. The description itself adds no parameter-level meaning, matching the baseline 3 when the schema already carries the burden.

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 'Upscales an image to higher resolution', a specific verb and resource, and it is distinct from every sibling (no other tool upscales). 'Returns a link to the upscaled image' also clarifies what the output is, so an agent can identify it 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?

The description implies usage when an image needs higher resolution, but it gives no explicit when-to-use/when-not-to-use guidance and names no alternatives. Prerequisite like the URL coming from fattly_upload_image is only in the schema, not in the description, so there is little help in choosing this over related generation/edit tools.

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