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

Annotations declare the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false), and the description adds genuinely new context: it costs 'one from the allowance,' returns a new design_id, and confirms the source design 'still exists.' The cost and non-destructive persistence behavior go beyond the structured hints.

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 tight sentences, front-loaded with the core action, then the semantic guarantee, then cost/return facts. Every sentence carries distinct information with no repetition of the schema.

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?

With annotations covering safety and no output schema, the description supplies the return value, the allowance cost, and the persistence guarantee an agent needs. Nothing critical is missing, though the visitor/design_id fallback semantics live only in the schema.

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%, so design_id fallback behavior, visitor, and instruction are already fully documented. The description's only parameter-adjacent detail is the return-value note, not new per-parameter meaning, so 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?

Specific verb+resource ('Redo an existing design') with concrete change examples (color scheme, detail level, lines, pose, words). It contrasts with the sibling design_item by noting they both 'spend one from the allowance' while this one operates on an existing piece, so an agent can tell them apart without opening either 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?

Clearly frames usage (revise a design that already exists, expected to stay 'recognizably the same piece') and references design_item as the parallel case. It stops short of an explicit when-not or a named alternative for creating a fresh design, so it is clear but not fully prescriptive.

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