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

With annotations all false, the description adds meaningful behavioral context: out-of-bounds rectangles are refused with the real image size rather than clamped, and there is a 4 MP limit for free sources. These are exactly the non-obvious runtime behaviors an agent needs.

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 with no filler: purpose, coordinate semantics, edge-case behavior, and a usage limit. Every sentence contributes information an agent needs before calling.

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 7-parameter mutation-like tool with no output schema, the description plus fully documented schema covers the required inputs, coordinate system, error behavior, and a key size limit. It does not explicitly describe the shape of the result, but out_path's schema description already covers the download link, so nothing critical is missing.

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 100%, so the baseline is 3, but the description adds useful semantics by defining (x, y) together as the top-left corner and explaining how out-of-bounds rectangles are handled. It complements rather than repeats the schema definitions.

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 uses a specific verb and object – 'cut a rectangle out of an image' – which is unambiguous and naturally distinct from sibling tools like image_resize, image_thumbnails, or image_convert. Even without naming a sibling, the action of cropping is precisely identified.

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?

It explicitly frames the tool as the action to take when a rectangular crop is needed ('Call this tool to cut a rectangle...'). It does not name alternatives or state when not to use it, so it stops short of a full 5, but the usage trigger is clear.

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