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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description reconciles with them by making clear no server-side payment occurs: the user pays in their browser and the reference identifies that payment afterward. It adds substantial context beyond the annotations (prices, currency, Stripe, no account required, fallback behaviour), though it does not say whether repeated calls mint multiple references or whether the reference expires.

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 tight sentences, front-loaded with the action and the return contract; the pricing/provisioning details are grouped in a parenthetical colon-list rather than padded into prose. Every clause earns its place.

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?

With zero parameters, no output schema and only coarse annotations, the description does the heavy lifting: it covers the return payload, pricing options, payment provider, authentication-free flow, and the negative outcome. An agent has enough to call it and explain the result without guessing.

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 tool takes no parameters, so the schema carries no semantic burden; baseline is 4. The description adds relevant context about what the caller receives (links, currency, billing cadence, purchase reference) without inventing parameter semantics.

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 specific verb (start/begin) and resource (Coast Map Pass purchase) and immediately describes what the call produces: checkout links tagged with a purchase reference, or a not-on-sale-yet signal. It is clearly distinguishable from siblings like coast_map_pass or pass_status, which do not initiate a purchase.

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?

Use context is implied (initiate a purchase from within the conversation, user completes payment in browser) but there is no explicit when-to-use versus when-not, and no pointer to siblings such as pass_status for checking an existing pass. The 'not on sale yet' fallback hints at a precondition without stating it.

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