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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explicitly states that the tool emails by default (controllable via the 'email' boolean), returns a number/due date/PDF link, and charges nothing, with the paid invoice appearing automatically after top-up. It does not cover error conditions or idempotency, but given the simplicity, it discloses the key behaviors well.

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?

The description is a single, dense sentence that front-loads the core action and then packs in defaults, return values, and payment flow with no wasted words. Every clause adds necessary information, making it appropriately concise and well-structured.

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?

Given the tool's simplicity, the description covers everything an agent needs: the action, parameters (amount, to, email) with defaults, return values (since there's no output schema), and the payment/posting behavior. There are no obvious gaps that would prevent a 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?

The schema already covers 100% of parameters with descriptions, so the baseline is 3. The description adds value by specifying the amount range (1–100000) not in the schema, clarifying the 'to' default (invoice email or account email), and confirming the 'email' default is true. This goes beyond the schema without redundancy.

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 opens with a specific verb and resource ('Issue a proforma invoice') and immediately scopes it to an 'UPCOMING balance top-up' with an amount range (1–100000). It also names the return values (number, due date, PDF link) and clarifies it charges nothing, making its function unambiguous and clearly distinct from sibling tools like send_invoice or list_invoices.

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 provides clear usage context: it's for creating a proforma for a planned top-up, with a default email behavior and an optional 'to' recipient. It explains that payment happens separately at rixot.com/add-funds, which implies when to use it (before payment). However, it does not explicitly name alternatives or state when NOT to use it, so it stops short of full guidance.

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