Free. Opens a Stripe Checkout Session for one card package and returns its payment link and its session id. This tool charges nothing and produces no artefact: on the card rail the thing that taps is a human. The package's work runs only at its redeem path, after Stripe's own record says that session is paid.
| Name | Required | Description | Default |
|---|---|---|---|
| sku | Yes | The SKU of the package, as list_card_packages publishes it, e.g. document_fact_audit. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes well beyond the annotations by resolving the counter-intuitive semantics of a 'buy' tool: it charges nothing, produces no artefact, a human completes payment, and the package's work only runs at the redeem path after Stripe records payment. That is exactly the non-obvious behavioral context an agent needs, and nothing contradicts the readOnlyHint=false/openWorldHint=true flags.
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?
Front-loads the surprising constraint with a one-word 'Free.' and stays to four sentences. Slightly literary phrasing ('the thing that taps is a human') costs a little density but each sentence carries real 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?
With no output schema, the description still names the return values (payment link and session id), and annotations cover the read/write and open-world profile. Nothing material for correct invocation 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% and the single sku parameter is fully documented in the schema, including its format and an example. The description adds no parameter-level detail, so the baseline 3 applies.
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: opens a Stripe Checkout Session for one card package, and names what it returns (payment link, session id). It is distinguishable from list_card_packages and verify_package, though it never explicitly contrasts itself with those siblings.
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 (call it to obtain a payment link for a package that list_card_packages published), and the redeem-path sentence hints at lifecycle, but there is no explicit when-to-use / when-not-to-use statement or named alternative for validating or listing packages.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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