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

Annotations already establish that this is a non-read-only, non-destructive, closed-world write. The description adds real value with the pricing and credit-conversion semantics (1,000 credits per $1, tier prices), but says nothing about link expiry, idempotency, or whether a subscription is created.

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?

A single front-loaded sentence with the action first and the reference data confined to a parenthetical. Dense but every clause is informative; no filler.

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 one-parameter tool this covers purpose, valid inputs, and pricing adequately. The notable gap is the return value: with no output schema, the description never indicates what the checkout link looks like or how long it remains valid.

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 enum is self-explanatory, so the schema carries the baseline. The description still adds meaning the schema lacks by mapping each plan id to its price and credit value, though it adds nothing about the required/optional distinction.

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 and resource ("Create a checkout link for a monthly plan") that is clearly distinguishable from sibling tools such as create_topup_link and get_referral_link. It does not explicitly name those alternatives, so it stops short of a 5.

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 parenthetical "plan ids from get_billing" gives a useful prerequisite and points at the sibling that supplies valid inputs. However, it never says when to prefer this over create_topup_link or what to do if the customer wants a one-time credit purchase, so usage is only implied.

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