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

With annotations already declaring destructiveHint, non-idempotent, and openWorld, the description still adds meaningful context: the effect is deferred ('nothing is charged until the maker opens the link and pays in the browser') and the output includes a price. It does not explain why the call is flagged destructive or that repeated calls produce separate sessions, but the key safety nuance is covered.

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, both earning their place: the first defines the return value and the upgrade effect, the second pre-empts the obvious concern about immediate billing.

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 tool returns a link rather than performing the charge, and the description makes that clear; an output schema exists so return details need no further explanation. Missing only failure modes such as an ineligible or already-Premium listing.

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?

Only one parameter with 100% schema coverage, including the pattern and a pointer to my_listings as the source of the slug. The description adds the constraint that the slug must be a live Free listing, which is the one bit of meaning beyond the schema.

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, resource, and return value ('Returns a Stripe Checkout link that upgrades one of your live Free listings to Premium, with the price'). The scope ('live Free listings') helps separate it from update_listing, though no sibling is named explicitly.

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 precondition 'live Free listings' implies when the tool applies, but the description never states what to do for an already-Premium listing or that update_listing is the tool for editing listing content. Usage is inferable rather than explicit.

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