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

Annotations only declare non-readOnly and non-destructive, so the description usefully adds behavior: autosend emails each generated invoice to the client, and disabling stops repetition. It doesn't disclose permission requirements or exactly what disabling clears, but adds meaningful context beyond the annotations.

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?

Three sentences, front-loaded with purpose then the actionable parameter guidance. Nearly every clause earns its place, with only minor redundancy between the id instruction and the surrounding prose.

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 6-parameter mutation tool with no output schema, the description covers the primary call path and the autosend side effect. It leaves some gaps (return behavior, what disable does to existing generated documents) but is sufficient for correct invocation.

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?

With only 50% schema coverage, the description compensates by explaining id derivation, the meaning of enabled true/false, the frequency pairing with day_of_month/weekday, and the semantics of autosend. This adds real meaning beyond the raw schema fields, though it doesn't fully cover all six parameters.

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 set (set up/update/disable) against a clear resource (recurring schedule on an invoice) with the outcome ('so it repeats automatically'). It is distinguishable from set_recurring_contract and trigger_recurring_invoice because it names the invoice as the target.

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 operative guidance, especially the routing instruction to derive the id via list_documents by number rather than asking the user. It stops short of explicitly saying when to prefer this over sibling tools like trigger_recurring_invoice, so no exclusion criteria are stated.

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