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

Annotations are all negative hints, so the description carries the disclosure burden. It does reveal the registration action, the free-tier limit of 3 unpaid invoices, and the output schedule, adding value beyond the annotations. However, it does not mention duplicate handling, what happens if the same invoice is already registered, or whether the action can be undone, which are meaningful gaps for a state-changing tool.

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 tight sentences: the first front-loads the action, required inputs, and output; the second states the limitation. Every word earns its place, with no fluff or redundancy.

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?

The description covers required inputs, the high-level return value, and a relevant constraint (free tier), enough for an agent to make a correct basic call. It omits optional parameters and duplicate_ok behavior, but these are already explained in the schema. The absence of an output schema means a more precise return-structure note would help, though the current description is largely adequate.

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 90%, so most parameters are already documented with detailed descriptions. The description re-iterates 'amount in integer cents' but adds no new parameter-level meaning beyond what the schema provides, so the baseline of 3 applies.

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 ('register') and clearly identifies the resource ('an unpaid invoice') and the return value (the three-letter escalation schedule with dates). It is inherently distinguishable from sibling tools like invoice_delete and invoice_status because it initiates a chase rather than deleting or querying a status.

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 a clear trigger context: 'Start chasing an unpaid invoice.' It does not explicitly name sibling alternatives or state when not to use the tool, so the guidance is useful but not exhaustive.

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