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

Adds substantial context beyond the annotations: resulting states (partially_paid / paid), the balance ceiling and keep_excess escape hatch, refund semantics, posting to the books, and a per-call price with failure being free. That is exactly the kind of financial/side-effect disclosure annotations cannot carry.

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?

Front-loaded with the core action, then constraints, then cost — a sensible order with little waste. The 'like Xero's' aside is slightly noisy, but the density is earned for a money-moving tool.

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?

No output schema exists, yet the description states the resulting invoice status and the cost/failure behavior, covering what an agent needs before calling. It omits what the call returns (e.g. payment id) and any repeat-call/idempotency guidance despite idempotentHint=false.

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 71% and the description reinforces the two highest-risk parameters (negative amount = refund, keep_excess = customer credit via invoices_use_credit). The note parameter's purpose remains unexplained in both places, which keeps it off 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?

States a specific verb+resource ('Record money received against a sent invoice') and enumerates the fields captured. It is clearly distinguishable from invoices_use_credit and invoices_record_prepayment, and even names the credit-use sibling for the overpayment case.

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?

Explains the precondition ('against a sent invoice'), the refund path (negative amount) and the overpayment path (keep_excess). It does not explicitly say when to prefer invoices_record_prepayment or invoices_use_credit instead, so routing is clear but not fully disambiguated.

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