pay_invoice

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

With no annotations, the description carries the full burden of behavioral disclosure. It only mentions the amount requirement and does not disclose potential side effects like wallet debit, irreversibility, or authentication requirements, making it insufficiently transparent.

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 extremely concise, with two short sentences that front-load the core action. No filler or redundant wording is present.

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 is minimal, lacking information about return values, error conditions, prerequisites such as sufficient balance, or guidance on when to use this tool versus the many sibling payment tools. While the schema covers parameters, the tool's behavioral aspects are under-specified.

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 provides descriptions for wallet_id and payment_request (67% coverage), and the description adds a constraint about the invoice amount. The memo parameter remains completely undocumented, and the description does not clarify its purpose or formatting.

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 clearly states the verb 'Pay' and the resource 'Lightning invoice', making the action unmistakable. It also distinguishes from siblings like pay_invoice_with_amount by noting the invoice amount must be included.

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 sentence 'The invoice amount must be specified in the invoice' provides a clear prerequisite, implying this tool is for fixed-amount invoices rather than amountless ones. However, it does not explicitly name alternative tools or describe when not to use it, leaving some ambiguity.

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