buy_credit_pack

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

The description discloses key behaviors: it initiates a payment via Stripe Checkout, credits are added instantly after payment, and credits never expire. With only a destructiveHint annotation (which is vague), this adds meaningful context about the transaction flow and post-payment effects.

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?

Four sentences, each earning its place: purpose, return value, pack options with pricing, and usage alternatives. Information is front-loaded and there is no redundancy or fluff.

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 simple one-parameter tool, the description covers all essential aspects: what it does, what it returns, available options, post-payment behavior, and related tools. With an output schema present and little ambiguity, this is complete.

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 schema already fully describes pack_id with allowed values. The description adds direct value by mapping each pack ID to its credit amount and price, making it easier for an agent to choose the right pack without external lookups.

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 states the tool's function with a specific verb ('Purchase') and resource ('credit pack'), and specifies it returns a Stripe Checkout URL. This distinguishes it from siblings like list_credit_packs and get_credits.

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?

Explicitly provides when-to-use guidance: suggests using list_credit_packs for current pricing and get_credits to check balance first. This frames the tool within the broader workflow and distinguishes it from alternatives.

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