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

With no annotations, the description carries the full behavioral burden, and it does so thoroughly. It discloses that the tool 'NEVER charges anything itself,' that payment happens on the Stripe page with user approval, that a key is optional, and that `confirm` verifies payment and activates the plan. This is exactly the kind of side-effect and flow context an agent needs.

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?

The description is long but every sentence earns its place: it front-loads the core purpose, then explains safety, usage triggers, key behavior, and post-payment confirmation. There is no filler or repetition; the structure moves naturally from what to how to when.

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 two-parameter tool with no output schema and no annotations, this description is remarkably complete. It explains the no-argument listing mode, the checkout-link flow, the payment page, account creation behavior, and the confirm step with its API-key result. An agent has everything needed to call the tool correctly in all intended scenarios.

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?

Although the schema covers both parameters, the description adds crucial semantics beyond the raw schema: omitting `plan` lists what is on sale, and `confirm` must be the 'WHOLE' checkout_id, potentially with a second part after a dot, and it reports payment status. This transforms simple property names into actionable instructions.

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 opens with a specific verb and resource: 'Buy a Polyfork plan: Pro (monthly or yearly) or a one-payment lifetime seat.' It also clarifies the tool's actual role—returning a Stripe Checkout link rather than charging—so an agent can distinguish it from a direct payment tool. This is far beyond a tautology and clearly identifies what the tool does.

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 explicitly states when to use the tool: 'Use it when a download needs a plan the user does not have and they say they want it, rather than sending them off to find the pricing page.' It also gives concrete usage patterns for both modes: calling with no arguments to list sale prices and calling again with `confirm` after payment. This leaves no ambiguity about when or how the tool should be invoked.

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