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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds genuine behavioral context beyond that: what comes back (a url plus an 'available' flag) and the important caveat that credit sales may not yet be open — information an agent cannot infer from the annotations.

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 core is front-loaded and short, but the text is duplicated verbatim in English and Chinese, including a repeated 'coming soon' notice. Roughly half the tokens carry no new information for an English-reading agent.

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 single optional-parameter, read-only tool with no output schema, the description covers what the call returns (url, available) and the sales-not-open state. Only minor gaps remain, such as currency or whether the URL expires.

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 0% and the parameter has no description, so the description must compensate — and it does, explaining that amount_cents optionally pre-fills the payment amount and must be a positive integer, which is exactly the semantic an agent needs. It stops short of clarifying units or currency, so not a 5.

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?

The description states a specific verb and resource — fetching a credit-purchase payment link — and pins it to a concrete URL (https://madecheck.com/credits/buy). It is distinguishable from sibling get_credit_balance, though it never names that sibling to make the contrast explicit.

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?

Usage is implied: call this to obtain a payment URL for buying credits. The 'Coming soon / 即将开放' note hints that sales may not yet be open, but there is no explicit statement of when to prefer this over get_credit_balance or pay_style_topup.

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