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

Annotations already declare openWorldHint=true and readOnlyHint=false, and the description is consistent with that: it explains that payment happens outside the agent in a browser and that the connection is upgraded as a consequence. That consequence-of-payment detail is genuinely beyond the annotations, though it doesn't cover failure cases, link expiry, or what state the connection is in before payment.

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?

Three short sentences, front-loaded with what is returned, then the agent's action, then the prerequisite. No repetition of name or title and every clause carries information the agent needs.

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?

No output schema exists, and the description correctly tells the agent that the return value is a URL to hand off rather than data to interpret. What is missing is post-conditions in more detail, such as how to confirm the upgrade succeeded or what the link's validity window is.

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?

The tool takes zero parameters, so there is no parameter semantics to explain and the baseline of 4 applies. Schema is empty with additionalProperties=false, matching the description's claim that nothing needs to be supplied.

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 ('Returns a checkout link for Aura Pro') plus the concrete commercial terms ($20/month, 500,000 requests). This is unmistakably distinct from every sibling, which are all read-only data retrieval tools.

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 a real precondition ('Needs a verified email first') and an explicit handoff instruction ('Give the link to the user'), which frames this as a human-in-the-loop escalation. It stops short of naming the sibling tools that satisfy the precondition (aura_verify_email / aura_claim_email), leaving that routing to inference.

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