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

Annotations already declare readOnlyHint=true, so safety is covered; the description adds genuine behavioral context by describing the returned record shape (customer, frequency, due_from, next copy, copies made, enabled state) and that an id lookup reveals the series even when stopped. It omits pagination/limits and result ordering, which keeps it from a 5.

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?

Two sentences, front-loaded with the resource and its payload, followed by parameter routing. The field enumeration is dense but each item earns its place; 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 a read-only two-optional-param list tool with no output schema, the description compensates by naming the fields returned, so an agent knows what to expect. Missing detail on result volume/limits and default no-param behavior keeps it below 5.

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% and both parameter descriptions are already detailed, so the baseline is 3. The description restates the clientid/id dual-mode but adds only marginal meaning (the due_from explanation of which invoice drives the next due date), so it does not exceed the schema significantly.

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 (List) and resource (repeat-invoice series) and then enumerates exactly what each series carries: customer, frequency, due_from, next copy, copies made, on/off state. An agent can distinguish this from list_invoices and list_payrun_schedules without opening any schema.

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?

Explicitly explains the two selection modes: clientid for one customer's series, id (invoice or any copy) for the series behind it. It does not explicitly contrast with the sibling list_invoices or note that omitting both params lists everything, but the contextual guidance for each parameter is clear.

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