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

Annotations cover only readOnlyHint and openWorldHint, and the description adds substantial context beyond them: the 0.05 USDC cost on Base, the fact that it does not analyze, sign, or charge, and what it returns. These are exactly the behavioral facts an agent needs before committing to a paid flow. It stops short of explaining what the returned payment instructions look like.

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?

Five short sentences with the risk-finding purpose front-loaded and the payment/behavioral caveats grouped after it. The opening 'Find open contours and self-intersections' reads like analysis and is only negated two sentences later, creating mild internal friction.

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 payment-preparation wrapper with no output schema, the description does explain the return payload and cost, which is the right focus. It leaves the entire input contract unexplained, which is a real gap for a tool with four required, zero-documented parameters.

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 0% for four required parameters (paths, minSegmentMm, nearNodeMm, closeGapMm), and the description never mentions any of them. Only the vague phrase 'supplied input' hints that caller data is echoed back, leaving thresholds and path structure entirely undocumented.

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?

The description names specific operations (open contours, self-intersections) and the concrete deliverable (a paid HTTP request, canonical endpoint, payment instructions), so the agent knows what it produces. It never names or contrasts the sibling prepare_* tools, so differentiation is left implicit.

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?

The phrase 'before cutting' supplies a usage window and 'not CNC certification' sets a boundary on interpretation. There is no explicit when-not guidance or routing to alternatives such as prepare_curve_clearance, so the agent must infer which prepare_* tool applies.

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