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

Goes well beyond the annotations (destructiveHint, non-idempotent) by disclosing that the operation is irreversible with no undo, that it refuses with masked/foreign filters, that large targets can take tens of seconds, and that a timeout restarts the session and loses unsaved work. It also notes the workspace pixel-limit constraint on the result.

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?

Front-loaded with the core purpose and sibling distinction, then layers refusal conditions and timeout risk in a logical order. Efficient per sentence, though the checkpoint advice appears twice ('when in doubt' and 'before an aggressive resize'), a minor 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. The description covers everything else an agent needs for a destructive, timeout-prone mutation: reversibility, refusal conditions, ordering constraints, and the workspace pixel limit.

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 width/height/long_edge descriptions already carry the semantics. The description restates the same rules (width+height stretches, one alone keeps aspect, long_edge targets the longer side) without adding new syntax or format detail, so the 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 and resource ('Scale the whole photo up or down') and immediately distinguishes itself from the sibling 'crop' by name. An agent can tell resize apart from crop, canvas_size, and transform_image without opening any 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?

Names the alternative to avoid ('not a crop, use crop'), spells out the exact parameter combinations for the three scaling modes, and states explicit preconditions and refusals (masked filters, filters made outside Editmamei). It even prescribes the ordering: resize before adding masked filters, not after.

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