pay_invoice

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

With no annotations provided, the description carries full burden for behavioral disclosure. It states 'Pay a Lightning invoice' which implies a financial transaction, but doesn't clarify if this is irreversible, requires authentication, has rate limits, or what happens on success/failure. This is inadequate for a payment tool with zero annotation coverage.

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, efficient sentence with zero wasted words. It's appropriately sized for a simple tool with one parameter and gets straight to the point without unnecessary elaboration.

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 payment tool with no annotations and no output schema, the description is insufficient. It doesn't explain what happens after payment (success confirmation, error handling), doesn't mention security implications, and provides minimal behavioral context despite the tool's financial nature.

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 input schema has 100% description coverage, with the 'invoice' parameter documented as 'BOLT11 Lightning invoice'. The description doesn't add any additional meaning beyond what the schema provides, such as format examples or validation requirements, so it meets the baseline for high schema coverage.

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 action ('Pay') and target resource ('a Lightning invoice'), making the purpose immediately understandable. It doesn't differentiate from siblings like 'decode_invoice' or 'get_transaction', but it's specific enough to understand what the tool does.

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 no guidance on when to use this tool versus alternatives like 'decode_invoice' or 'validate_address'. It doesn't mention prerequisites, such as requiring a valid invoice or sufficient balance, leaving the agent to infer usage context from the tool name alone.

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