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

Goes well beyond the annotations: discloses that line items are snapshotted at creation time, that each generated invoice is left as draft/published-link/emailed per action, and that omitting confirm yields a read-only preview rather than a mutation. These are exactly the side-effect details an agent needs given destructiveHint=true.

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, and every sentence carries information with no filler. It is a dense paragraph rather than structured bullets, which slightly hurts scannability for eight parameters, but nothing is wasted.

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 an 8-parameter mutation tool with no output schema, the description covers side effects, the confirm gate, and copying semantics thoroughly. It doesn't say what the preview result contains or what errors look like (e.g., voided/estimate invoice ids), leaving a small gap.

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 already 88%, so the baseline is 3; the description adds real value by tying interval/every/nextDate together ('every N weeks, months or years from nextDate') and clarifying endAfter as a cap. It doesn't further explain paymentTermsDays or invoiceId eligibility beyond the schema text.

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?

Specific verb+resource ('Makes an invoice repeat') plus the exact mechanics: same client, lines, tax, notes and terms recurring every N weeks/months/years. It clearly distinguishes this from create_invoice (one-off) and update_recurring_invoice (modify an existing schedule) by describing creation of the recurring arrangement.

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 operating context: 'Pro' plan gating, the confirm:true requirement with a preview fallback, and the action choice (draft/send/email) with the email precondition. It does not explicitly route the agent away from create_invoice or update_recurring_invoice, so it lacks named alternatives, but the when-and-how context is strong.

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