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

With no annotations provided, the description carries the transparency burden. It discloses the cost model ('Free — no credits required') and an important security requirement ('Proof of npub ownership is required to prevent credit-grant front-running'). This goes beyond a generic read operation, though it does not describe all possible side effects or response behavior.

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 compact and front-loaded with the core purpose, followed by a single usage directive and two key behavioral constraints. Every sentence earns its place with no redundant phrasing.

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 combination of a clear purpose, explicit sequencing after purchase_credits, cost information, authentication context, and a complete input schema is sufficient for correct invocation. The presence of an output schema reduces the need to describe return values. Minor missing details like polling behavior or possible statuses are covered by the output schema.

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 parameters are already fully documented. The description adds contextual value by tying the call to purchase_credits and mentioning proof of ownership, but it does not need to restate the parameter details. This 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 states a specific action: 'Check the payment status of a Lightning invoice.' It further anchors the tool in a concrete workflow by saying 'Call after paying the invoice from purchase_credits', which distinguishes it from sibling status/check tools like check_balance, check_price, and check_proof_status.

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 gives explicit when-to-use guidance: 'Call after paying the invoice from purchase_credits.' It also adds practical constraints such as being free and requiring proof of npub ownership. It does not explicitly name alternatives or exclusions, but the workflow placement is clear enough.

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