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

Annotations already declare readOnly/idempotent/non-destructive, and the description reinforces rather than contradicts them by stating the tool "does not design anything, does not use credits and does not mean a part exists" — exactly the misconception an agent might form from the name. It additionally discloses auth and credit requirements that live only in prose, plus how the brief is assembled from the inputs.

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?

Four sentences, each load-bearing: what it builds, how the brief is composed, what it does not do plus prerequisites, and the sibling alternative. The core action is front-loaded and there is no filler or repeated schema detail.

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 four-parameter, no-output-schema, low-side-effect tool this is essentially complete: it covers output shape (a URL), composition logic, prerequisites and the alternative path. Only a small gap remains — it does not explicitly instruct the agent to surface the resulting link to the user — which keeps it just below perfect.

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 per-parameter meaning (material affecting tolerances, dimensions format, enum export formats) is already documented, and baseline is 3. The description earns a notch above baseline by explaining that description + dimensions + material are merged with standard printability requirements into one brief, which clarifies how the four fields interact rather than restating them.

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 artifact ("Build a printpal.io link that opens the PrintPal AI CAD agent with a design brief prefilled") and names the exact user intent it serves. It is clearly separable from prepare_3d_generation and open_3d_generator_link by targeting the AI CAD agent for dimensioned functional parts.

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 an explicit inclusion condition (functional part with exact dimensions: bracket, enclosure, adapter, mount) and an explicit exclusion routing to a sibling ("For a figurine or other organic model made here, use prepare_3d_generation instead"). It also flags the downstream prerequisite of signing in and spending credits, so the agent knows this is a hand-off rather than a completed action.

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