pay_invoice

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

No annotations are provided, so the description carries full burden for a payment/mutation operation. It does not disclose irreversibility, fee behavior, authentication or wallet permission requirements, failure modes, or what a successful payment returns.

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 short sentences, front-loaded with the core action and followed immediately by the key precondition. There is no wasted text.

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 under-specified. It should explain payment result behavior, fee handling, irreversibility, and relevant sibling routing to be complete enough for safe 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?

Schema description coverage is 100%, so all three parameters are already documented in the input schema. The description adds only that the amount must be embedded in the invoice, which slightly reinforces the payment_request semantics but adds little beyond the schema.

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 and resource: 'Pay a Lightning invoice.' The constraint that the invoice amount must be specified distinguishes it implicitly from amountless siblings like pay_invoice_with_amount, but it does not name that sibling explicitly.

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 amount requirement implies when this tool applies versus amountless payment flows, but the description never explicitly says to use pay_invoice_with_amount for invoices without an amount, nor does it mention other alternatives such as pay_lightning_address or pay_lnurl.

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