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

Annotations already mark this as read-only and idempotent. The description adds useful behavioral detail beyond that: the checkout link opens Stripe Checkout, requires no login, and the tool never charges anything itself. This helps an agent set user expectations correctly.

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 deliver all essential information with no filler. The main purpose is front-loaded, and the key caveat about not charging is stated directly.

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 single-optional-parameter tool with a rich schema and an output schema present, the description sufficiently explains what the tool returns, how to handle the response, and what side effects (none, besides opening Stripe) the user should expect.

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 input schema already fully documents the single `pack` parameter, including enum values, credit amounts, prices, and default. The description adds only the general 'omit pack for suggested' behavior, which is already reflected in the schema's default note, so it provides marginal extra semantic value.

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 clearly identifies the tool's function: it returns links to buy more credits, including a Stripe Checkout link and the billing page. It is distinct from siblings like get_credits, which reads balance, and other run/project 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?

The description gives clear usage context: give the link to the user when they need to top up credits. It also clarifies that the tool itself never charges, and explains the default behavior when `pack` is omitted. It does not explicitly name alternatives, but no other sibling serves this top-up purpose.

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