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

Goes well past the annotations by disclosing the consent gate (server refuses while startNow is false), the no-charge-until-payment semantics, the renewal/expiry behavior of each offer, and the idempotencyKey retry contract. Note the annotations declare idempotentHint=false while the description offers key-based replay protection; these are compatible (the key makes retries safe, not the call itself), so no contradiction. No auth scope beyond owner/admin is described.

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 primary effect (page URL, deferred charge) leads, followed by the offer breakdown and then the constraints. It is a single dense paragraph with heavy parenthetical nesting, which costs a little readability, but every clause carries distinct operational information.

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 side-effecting, open-world, permission-gated checkout tool with no output schema, the description covers who may call it, what each offer does, what is returned (a URL), the consent precondition, and retry behavior. It does not address interaction with an existing subscription or what happens to concurrent/duplicate checkouts beyond the idempotency key.

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%, so the baseline is 3, but the description adds interpretation the schema lacks: quantity applies only to team_credits and is priced at the plan's per-credit rate, paid once and expiring with the plan month, while teamPlan turns the purchase into a renewing subscription. It reinforces the startNow refusal and idempotencyKey reuse semantics in prose.

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 ("Opens a payment page and returns its URL") and immediately scopes out what it is not (nothing is charged until the buyer pays). It also enumerates the three distinct purchase shapes, so an agent can tell it apart from request_more_credits or update_team_subscription without opening schemas.

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?

Gives real eligibility conditions: only a workspace on a plan may use team_credits, and only owners and admins can open a page. It also maps each offer to its use case (pack vs. subscription vs. top-up credits). It does not name sibling alternatives (request_more_credits, list_credit_offers, update_team_subscription) as explicit redirects, so it stops short of a 5.

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