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

Annotations declare readOnlyHint=false, destructiveHint=false, openWorldHint=true, so the agent knows a non-destructive external-facing object is created. The description adds genuinely new context beyond the annotations: the output is a URL the reader opens themselves, and 'nothing is charged by this tool' clarifies that charging happens outside this call — resolving the apparent tension with readOnlyHint=false.

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?

A single dense sentence with the product options front-loaded and the no-charge caveat last. Every clause carries information and nothing is padded.

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 one-parameter tool with no output schema, the description covers input meaning, the nature of the return value (a link), and the safety-relevant side effect boundary. Minor gaps remain around link expiry/reuse and whether checkout sessions can be created repeatedly.

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 0%, so the description must carry the load, and it does: it maps the three enum values to plain-language meanings (Plus monthly, Plus yearly, one market coverage). It doesn't clarify whether 'cover_one' requires selecting which market here or later in the browser flow, which is the remaining ambiguity.

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-equivalent (produce a Stripe checkout link), the resource (checkout link), and the exact products (Plus monthly/yearly, or one market coverage). It distinguishes itself from sibling cover_market by being a link generator rather than a purchase action, though it doesn't name that sibling explicitly.

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?

Usage is implied: the signed-in reader wants to pay and needs a browser URL. There is no explicit when-not or stated alternative (for example, whether cover_market should be used instead for directly acquiring a coverage), so the agent must infer routing.

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