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

Annotations already declare readOnlyHint=false and openWorldHint=true, and the description adds substantive behavior beyond them: nothing is charged until the person pays on Stripe, cards are provisioned to the given email only after payment, and redemption happens by signing in on tangylimes.com. It also pre-empts the most likely agent failure mode by forbidding claims that the purchase is complete — exactly the kind of non-obvious context annotations cannot convey.

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 sentences, front-loaded with what is produced and its price, followed by the payment/provisioning flow and then the critical display instruction. No filler, and the most important constraint lands last for emphasis.

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?

There is no output schema, and the description fills that gap by stating that the return value is a checkout link for the agent to show the user. For a three-parameter, non-destructive external-call tool, nothing needed to invoke it correctly 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 coverage is 100%, so the baseline is 3; the description earns a notch above by defining what a 'pack' means (3 cards at $4.99) and by tying the email parameter to the sign-in identity used on tangylimes.com. The optional 'code' discount parameter is not mentioned, which is the only gap.

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 opens with a specific verb and resource — 'Make a Stripe checkout link for packs of 3 cards' — plus the unit price, so the agent knows exactly what is produced. It does not, however, distinguish itself from the sibling 'make_card_link', which an agent could easily confuse with this tool.

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 context is clear: this is the path when someone wants to purchase cards in bulk, and the description adds an explicit operating instruction ('Always show the link to the person; never claim the purchase is done'). It stops short of naming alternatives such as get_pricing or make_card_link or stating when not to use it, so routing still requires inference.

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