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

Annotations already flag it as a non-read-only, open-world operation, and the description adds genuinely new context: credit cost range (25-200) tied to scale and mode, and that it returns a project id rather than a finished file. It does not mention the tier restriction on 4x or failure modes, keeping it below a 5.

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 filler, with the core operation front-loaded and the async handoff stated after it. Every clause carries information an agent needs.

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?

Output schema exists and the rich input schema covers parameters, so the description's job is mostly routing and cost signaling, both of which it does. It stops short of noting the Creator+ tier requirement for 4x or typical processing time, small residual gaps for a paid async job.

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 mode enums, the 2/4 scale constraint, the 4096px input limit, and credit multipliers are all already documented in the schema. The description only restates the 2x/4x option without adding syntax or defaults, so 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?

States a specific verb (upscales), resource (image), and constraint (2x or 4x), which cleanly separates it from upscale_video and the many create_* siblings. An agent can identify the operation 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 the use case (make an image larger/higher resolution) and points to wait_for_image_project for the async follow-up, but never states when to prefer this over edit_image or generate_image, nor any preconditions for input assets. Usage is inferable but not spelled out.

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