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

Annotations already declare a non-read-only, non-idempotent, non-destructive operation; the description usefully adds that the result is a link handed to a human rather than an automatic charge. It does not disclose the consequences of the non-idempotent hint (does calling twice create two payable links?), link expiry, or whether funds move before payment.

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 short sentences, zero filler, with the core action and the human hand-off requirement front-loaded. Nothing is repeated from the title or schema.

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 mutating two-parameter tool with no output schema and no read-only safety net, the description covers what is produced (a payment link) but omits link lifetime, what happens on repeat invocation, and whether a pending top-up already exists. It is adequate but leaves real operational gaps.

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 both parameters are already documented, including the 'range from topup_lookup' constraint. The description's 'wallet behind any Mailgi address' reinforces that address can be an alias and that it identifies an existing wallet, but adds no format or validation detail 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 and artifact ('Creates a card payment link') scoped to 'the wallet behind any Mailgi address', which is far more informative than the name alone. It does not explicitly contrast with topup_lookup or topup_status, so sibling differentiation is left mostly to the naming convention.

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?

'Give it to a human to pay' implies the human-in-the-loop flow and its intended purpose, but there is no explicit when-to-use guidance relative to topup_lookup (pre-check amount range) or topup_status (poll payment state). The reader must infer the sequence from sibling names.

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