pay_lightning_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. While it states this is a payment operation (implying funds transfer), it doesn't describe what happens on failure, whether payments are reversible, what permissions are required, or any rate limits. The mention of 'agent wallet funds' hints at spending policy enforcement but doesn't elaborate on what that entails.

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 that conveys the core purpose without unnecessary words. It's appropriately sized for a tool with good schema documentation and gets straight to the point with no fluff or redundant information.

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 minimally adequate. It identifies the core action and funding source but lacks important context about failure modes, return values, or operational constraints. The 100% schema coverage helps, but for a financial transaction tool, more behavioral context would be beneficial.

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 the schema already documents all three parameters thoroughly. The description doesn't add any parameter-specific information beyond what's in the schema descriptions, maintaining the baseline score of 3 for adequate coverage through structured data alone.

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 resource ('Lightning Network invoice') with the funding source ('agent wallet funds'), making the purpose immediately understandable. It doesn't explicitly distinguish from siblings like 'send_to_lightning_address' which might have overlapping functionality, but the specific mention of invoice payment provides good differentiation.

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 'send_to_lightning_address' or 'access_l402_api'. It mentions the funding source ('agent wallet funds') which implies a prerequisite of having wallet funds, but doesn't specify when this tool is appropriate versus other payment methods or what conditions must be met.

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