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

Annotations only declare readOnlyHint=false, openWorldHint=true, destructiveHint=false. The description adds real context beyond that: the tool merely mints a checkout link rather than charging, credits are non-expiring, and fulfilment is asynchronous ('added once payment completes'). It omits link lifetime and failure modes.

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, no filler: the action leads, the enumerable price data follows, and the handoff instruction closes. Nothing could be cut without losing required information.

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 what the agent most needs: what comes back (a link) and when the purchase actually lands. Minor gaps remain around link expiry and error/refund behavior.

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% and the enum is self-documenting, so the baseline is 3. The description goes further by mapping each allowed quantity to its price ($5/$15/$25/$50/$125/$250), which the schema does not contain and which an agent needs to answer user questions.

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: 'Creates a secure Stripe checkout link for a pack of non-expiring verification credits.' This is unmistakably distinct from every sibling (income/rent math, reports, verification requests), so an agent can select it without opening the schema.

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 an explicit workflow: create the link, hand it to the user, and credits land after payment completes. That tells the agent this tool does not itself complete a purchase. It stops short of naming alternatives or when-not-to-use conditions, so it falls short of a 5.

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