create_addfunds_invoice

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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the safety posture is largely covered. The description does add real value beyond them by flagging that this creates an actual monetary invoice; however it stops short of saying whether funds are captured immediately, whether it is reversible, or what the confirm flag protects against beyond the schema's own text.

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 tight sentences with no filler, and the key impact signal ('MONEY') is front-loaded. The parenthetical API path is arguably internal plumbing, but it is short and harmless.

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 money-moving mutation with no output schema, the description plus annotations cover the essentials: it writes, it's not read-only, it touches the open world, it creates a real invoice, and confirm must be true. It still leaves the agent guessing about downstream effects (payment capture, whether the invoice must be paid separately) and offers no routing hint to the sibling billing tools.

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 description coverage is 100% (amount is 'Top-up amount in account currency', confirm is 'Must be true to run the operation'), so the schema carries the parameter burden. The description only restates 'for the given amount' and adds no unit, currency, or range 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 resource ('Create an invoice to top up the credit balance') and even names the backing API operation (whmcs/create_addfunds), so the agent knows exactly what it does. It does not, however, differentiate itself from the many nearby billing siblings like apply_credit or generate_due_invoice, which is where confusion is most likely.

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?

There is no explicit when-to-use or when-not-to-use guidance, and no reference to alternatives such as apply_credit or mass_pay that also affect a client's balance. 'MONEY: creates a real invoice for the given amount' is a warning about impact, not a usage rule for choosing this tool.

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