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

Annotations already convey readOnlyHint, idempotentHint, and non-destructive behavior, so the bar is for added context. The description adds valuable behavioral detail: it does not charge anything and hands payment to the user's browser, plus it may return the plans page instead of a checkout link. This meaningfully clarifies side effects beyond the annotations.

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?

Two sentences with no filler, front-loading the core return value and immediately clarifying the no-charge behavior. Every clause earns its place, and the fallback behavior is included without redundancy.

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 simple two-parameter tool with full schema coverage and strong annotations, the description is nearly complete: it covers the return type, the no-charge side effect, and the fallback path. It could explicitly state the return shape (a URL string) or mention the tier default, but the schema already documents the tier, so nothing critical 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 description coverage is 100%, so the baseline is 3: the enum parameter descriptions already explain exam codes and the tier limitation to Part 107. The description itself adds no parameter-level detail beyond 'an exam', but because the schema is fully self-documenting, it does not need to.

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?

Description states a specific verb ('Returns') and resource (direct purchase link / Stripe Checkout for a named exam), and clearly distinguishes this from broader sibling tools by spelling out the exact deliverable. The fallback to the plans page adds precision about scope.

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 description implies when to use the tool: whenever a purchase link for a Rotate Pilot prep is needed, with a conditional fallback for exams without one-click checkout. However, it does not explicitly compare against sibling tools such as get_offer, so an agent must infer the boundary between them.

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