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

With no annotations, the description carries the burden and does add real behavioral disclosure: the resampling method (nearest neighbour, so no blurring) and a hard output constraint of 1024 px. It omits failure behavior, permissions, and what the response contains, but the two disclosed traits are the ones that most affect correct invocation.

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, zero filler, with the algorithm and the sharpness benefit front-loaded and the output cap as the closing constraint. Nothing repeats the title or name verbatim.

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 tool with no output schema, the description should say what comes back — the description gives only a size cap (1024 px) without output format, delivery (URL vs inline data), or how the two input parameters interact. It is adequate but leaves gaps an agent would hit at call time.

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 coverage is 67%, so baseline is 3. The description reinforces that scale must be a whole number but never states the permitted 2–64 range or the default of 8, and it says nothing about choosing image_url versus image_base64 — leaving the mutually exclusive input path entirely to the schema.

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 (scale up), resource (pixel art), and the exact algorithm (nearest neighbour, whole-number factor), which distinguishes it from the sibling pixelate_image at a glance. An agent can select this tool 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?

Usage is only implied by 'Scale pixel art up' — the agent must infer that this applies to already-pixelated input rather than photographic images. No explicit when-to-use, when-not-to-use, or reference to alternatives such as pixelate_image or remap_palette.

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