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

Annotations only declare the safety profile (readOnly=false, destructive=false, idempotent=false). The description adds copy-on-write semantics that the annotations cannot convey — a new design with its own id is returned and the original stays — plus a billing detail ('counts as one design'). This is meaningful context beyond structured fields.

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 action and required inputs, then examples, then return semantics. Slightly redundant — 'so the original artwork is kept' and 'the original stays' say the same thing — but every sentence still earns its place.

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 no output schema, the description correctly carries the return-value burden: a new design with its own id, original preserved, one design counted. Both parameters are required and documented, and the design-id lifetime ('works in any later turn of the chat') is clarified in the schema. Nothing an agent needs to call this correctly 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 both parameters are already fully documented, and the description mostly restates them (design id format d_..., change in plain words). The added example phrasings ('make the border gold') are marginally useful but do not extend beyond what the schema and usage text already cover, 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 ('Make a change to a design from this chat') and names the required inputs, so an agent knows this edits an existing design rather than creating one. It does not explicitly name the sibling design_patch to draw the boundary, but the 'from this chat' scope implies the create-vs-edit distinction.

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?

Gives clear context for use: a change the user asks for later in the chat, with the note that the original artwork is kept. It does not name alternatives (e.g., design_patch) or state exclusions, so the routing guidance is strong but not complete.

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