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

Annotations only mark this as non-read-only and non-destructive, so the description carries most of the behavioral burden. It adds meaningful context by explaining that the invoice 'repeats automatically' and that autosend emails generated invoices to the client, going beyond what the annotations alone reveal. It does not detail effects like overwriting an existing schedule or whether disabling preserves history, but the core behavior is disclosed.

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 three sentences with no filler: purpose first, then invocation guidance, then the autosend behavior. Every sentence adds actionable information, and the most important scoping detail ('on an invoice') is front-loaded.

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 six-parameter mutation tool with no output schema, the description plus schema covers the essential invocation details: required fields, frequency options, day-of-month/weekday defaults, and autosend behavior. It is complete enough for correct use, though it could be stronger by explicitly noting that enabled=false disables an existing schedule and by distinguishing trigger_recurring_invoice.

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 only 50%, so the description must compensate for undocumented parameters. It clarifies autosend and the frequency/day/weekday relationship well, but it only minimally explains 'id' and 'enabled' and could mislead by implying frequency is always required even though only id and enabled are required in 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?

The description uses a specific verb set ('Set up, update, or disable') tied to a clear resource ('a recurring schedule on an invoice'), so an agent immediately knows what the tool does. It also implicitly distinguishes itself from siblings like set_recurring_contract and trigger_recurring_invoice by focusing on invoice schedules and configuration rather than contracts or manual triggering.

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 description states the general use case and provides step-by-step invocation guidance, but it never explicitly says when to prefer this tool over related siblings such as trigger_recurring_invoice or set_recurring_contract. The usage context is clear, but exclusions and alternative routing are left to inference.

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