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

With no annotations at all, the description carries the full burden. It usefully discloses that the result is a link the human completes on Stripe's page and that promo codes are entered there, but it does not say whether the call charges anything, whether the subscription starts immediately, or how long the link stays valid.

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 purpose is front-loaded in the first sentence, followed by decision-relevant pricing. The tier recitation is somewhat redundant with the enum descriptions and could be trimmed.

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?

This is a simple 2-parameter tool with a fully documented schema and no output schema, so the bar is modest. Still missing are the lifecycle facts an agent needs to answer its human's follow-up questions: charge timing, subscription activation, and link expiry.

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 coverage is 100% and the plan enum already lists each tier's price, so the plan breakdown in the description largely duplicates structured data. The added value is the overage pricing ($0.15/min, $2/number, $0.015/SMS), which is not in the schema and helps the agent advise its human.

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?

States a concrete verb and resource: obtain a Stripe Checkout link for a monthly plan, which is distinct from manage_billing or account_usage. It never names the sibling it is closest to, so an agent must infer the boundary itself.

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?

'Give the link to your human' gives one clear follow-up action, implying this is an agent-to-human handoff step. There is no explicit when-to-use versus manage_billing, and no statement that sign_up/api_key must already exist before calling.

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