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

The description adds behavioral context by listing resize modes and aspect-ratio support, while annotations already indicate the tool is neither read-only nor destructive. It does not disclose output format, whether the original file is modified, or side effects such as default EXIF stripping, though some of this appears in the schema.

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?

The description is short and front-loaded, with only two content-bearing sentences and a category tag. The 'Resize Image —' prefix is somewhat redundant with the tool/title name, but the rest is efficient and free of filler.

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 nine parameters and full schema coverage, the description provides enough high-level context to select and invoke it correctly. The output is inferable as a resized image, and the missing return-format details are minor given the otherwise complete schema and clear operation.

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% with detailed parameter descriptions for every field, so the description carries little parameter burden. It provides high-level mode categories that map to the mode enum, but it adds no meaningful parameter semantics beyond what the schema already documents.

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 states a specific operation ('Resize an image') and enumerates the resizing strategies: pixel dimensions, percentage, fit-within-max, and exact canvas. This makes the tool's purpose clear and distinct from sibling crop/editor tools, though it does not explicitly name a sibling for contrast.

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 when to use the tool — when an image needs resizing — and highlights aspect-ratio support, but it does not explicitly say when to prefer this over photo_crop, photo_compress, or photo_editor, nor does it mention exclusions. Usage context is present but implied rather than explicit.

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