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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds real value beyond that: it flags the call as free, discloses that the id space is the entire Printful catalog (including hats, contradicting the 'curated' framing when an id is given), and enumerates the per-mode payloads (US in-stock sizes, placements in inches, embroidery thread colours).

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 cost signal ('Free.'), then the two modes, then the routing purpose. Every clause adds decision-relevant information; no filler or repeated name/title.

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 must cover returns, and it does so for both modes with concrete fields. It is complete enough to call correctly; only minor gaps remain (no mention of response size or whether the curated list is paginated).

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 baseline is 3. The description earns above baseline by interpreting the parameter's two regimes (absent = curated list, present = any Printful catalog id including hats) and the shape of what each mode yields, which the schema's one-line description does not convey.

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 the resource (print-on-demand garments, colours, print areas) and precisely distinguishes its two operating modes: without garmentId returns the curated list, with garmentId returns colours/sizes/placements. The agent can identify what it returns without opening anything else.

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?

Explicitly routes the agent: 'Use it to pick garmentId, color and placement for aetherwave_merch_mockup.' It names the downstream sibling and the exact function this call serves, so when-to-use versus aetherwave_merch_mockup is unambiguous.

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