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

The annotations already declare readOnlyHint=true, and 'Read-only' merely repeats that, earning no extra credit. What the description does add is beyond the annotations: the shape of the returned schedule data (frequency, next send date, remaining cycles), which is useful when no output schema exists. It stops short of explaining pagination or sort behavior for a list endpoint.

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 short sentences, front-loaded with the resource and its returned fields, then the safety note and the raw API endpoint. Every sentence carries information, though the GET path is marginal value for an agent that only invokes the tool.

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 list tool with no output schema, the description adequately covers what is returned and the read-only nature, and the schema fully carries the filtering parameters. The missing piece is pagination/filtering guidance, which matters given seven optional filters and no defaults stated.

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 all seven parameters (page, per_page, sort, number, status, client_id, client_status) are already documented in the schema with examples and ranges. The description adds nothing about parameter semantics, so the baseline of 3 is appropriate.

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 a specific resource (recurring invoice schedules), and names the salient returned fields (frequency, next send date, remaining cycles). The word 'recurring' cleanly separates it from the sibling invoiceninja_list_invoices, so an agent can pick it without opening the 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?

The description gives no when-to-use guidance, no mention of alternatives such as invoiceninja_list_invoices, and no note about pagination or filtering strategy despite seven available filter parameters. Usage is only implicit from the verb.

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