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

Beyond annotations, it discloses that the user performs payment in the browser, that an active subscription is switched in place and prorated, and that access is only granted via the payment webhook. This materially changes how an agent should handle the returned URL and follow-up.

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 dense sentences with the primary purpose front-loaded. Every sentence carries operational information: what is returned, how the user pays, what happens on an existing subscription, and what to call next.

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 return variants are described explicitly, the payment flow is specified, and the follow-up call to get_account is provided. With no output schema, this description gives an agent enough behavioral context to select and invoke the tool correctly.

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 covers all three parameters, so the baseline is 3. The description adds useful pricing and billing-period context for plan and interval, although confirm is not mentioned in the description; the schema covers its meaning.

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: it returns a Stripe Checkout URL for a named plan. It also gives concrete pricing and the active-subscription alternative (settings URL), so there is no ambiguity about what this tool produces.

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?

It gives clear context: the user opens the URL and pays, the agent must never enter payment details, and after payment the agent should call get_account. It does not explicitly state when not to use the tool or compare it to alternatives, but the workflow guidance is strong.

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