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

Beyond the annotations (which already declare non-destructive, non-read-only), the description adds two useful behavioral facts: the source file is left unchanged, and the call is asynchronous, returning a toolExecutionId that must be polled via get_tool_execution. These are concrete details not derivable from the structured fields.

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 core action, then the async return contract, then the non-destructive guarantee. No filler or redundancy.

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?

An output schema exists so return values need not be explained, but the description still usefully covers the async lifecycle (toolExecutionId → get_tool_execution → output file), which is the key operational detail for calling this tool correctly. Missing only explicit routing guidance versus sibling transform tools.

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 single parameter (imageFileId) is fully documented in the schema with sourcing hints. The description adds no further parameter-level meaning, so the baseline 3 is appropriate.

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 specific verb and resource ('Create a higher-resolution copy of an existing image') and states the intent ('for sharper presentation'), so an agent can immediately tell what it does. It does not, however, differentiate itself from adjacent siblings like vectorize_image or image_3d_effect, which are other image-transform operations.

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 only implied by the name and purpose — there is no explicit guidance on when to choose upscale_image over alternatives such as vectorize_image, image_3d_effect, or upscale_video. No when-not conditions or prerequisites (e.g., required input type) are stated.

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