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

The description goes well beyond the annotations by revealing asynchronous delivery, the need for the record to still exist at delivery, deletion/voiding as failure causes, the fact the email cannot be unsent, and the Caribooks approval requirement. This gives the agent crucial behavioral expectations that annotations alone do not provide.

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 description is efficient and every sentence contributes: the action, the asynchronous timing, the record-existence caveat, and the irreversible approval step with a direct URL. The most important information is front-loaded at the start.

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?

The description is complete for an irreversible, side-effectful, externally-delivering tool. It covers what happens after calling, why approval is required, what can prevent delivery, and what the agent should tell the user. With no output schema, no additional return-value explanation is needed.

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%, so the schema already fully documents id, email, company, and confirm. The description adds useful context around delivery and approval but does not meaningfully elaborate on the individual parameters beyond what the schema says, matching the baseline for full schema coverage.

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 opens with a specific action and resource: 'Email the customer a receipt for a payment received, as a PDF from QuickBooks Online.' This clearly distinguishes it from sibling send_* tools by focusing on payment receipts, not invoices, credit memos, or sales receipts.

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?

The first sentence implies the tool's intended use case, and the approval/confirmation context explains when the email actually goes out. However, it does not explicitly compare against alternatives or state when this tool should or should not be chosen over sibling send_* tools, so the guidance is mostly implied.

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