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

Annotations only declare the write/non-destructive/open-world profile; the description adds substantial context beyond them: partial payments allowed unless Progress Invoicing requires the full amount, card-on-file auto-use that always notifies the customer, the per-call confirmation default, and the required Cotlet API key scope.

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-loads the core action and is generally tight, with the key operating constraints sequenced well. Minor redundancy ('optionally sending the customer a receipt' vs 'an optional receipt email') costs it a perfect score.

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 write tool with no output schema, it covers the action, edge cases (partial payment, card on file), confirmation behavior, and auth requirements. Nothing an agent needs to invoke it correctly is missing.

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 the schema alone carries parameter meanings (baseline 3). The description adds genuine semantics for amount by stating the partial-vs-full constraint under Progress Invoicing, which the schema does not convey.

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 ('Apply a payment to an open invoice') and immediately frames it against the in-product analog ('the same as Pay in the invoice preview'), so the agent knows exactly what operation this is. It is distinguishable from housecall-pro siblings like send_invoice, create_progress_invoice, and get_invoice.

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?

Gives clear context for use: applying a payment to one open invoice, with the receipt-email option. It does not name alternative tools or explicitly state when-not-to-use, so it falls short of a 5, but the operating condition is unambiguous.

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