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

With no annotations, the description carries the burden of behavioral disclosure. It explicitly says the tool does not move money, requires a session or Stripe checkout, and mentions terms, idempotency, and metering. This is significantly more transparent than a typical mutation tool description, though it does not detail error behavior or auth beyond the session note.

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?

Two sentences deliver dense, useful information with the main purpose front-loaded. The endpoint details, behavioral caveat, and prerequisite are all stated without wasted words.

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?

The description covers purpose, endpoints, idempotency, metering, and the session/checkout requirement, which is good for a call with no output schema. But it does not specify how to choose between the two endpoints, what values tier accepts, or what the response contains, so it is not fully 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?

Schema description coverage is 0%, so the description must compensate. It maps the call to 'product and tier,' which aligns with the slug and tier parameters, and distinguishes one-time vs subscription paths. However, it does not explain valid tier values, endpoint selection criteria, or slug format, leaving meaningful gaps.

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 performs a purchase for a product and tier, and gives concrete endpoint paths for one-time packs and subscriptions. It is specific and not a tautology, though it does not explicitly name sibling tools to draw the distinction beyond calling itself 'the exact purchase call'.

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 context: this is the purchase call, with different endpoints for one-time vs subscription, and it requires a session or Stripe checkout. It does not explicitly list alternatives or exclusion conditions, but the framing strongly implies when this tool should be used.

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