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

With no annotations, the description carries the behavioral disclosure burden. It discloses cost, required ownership proof, and the front-running prevention rationale, which implies the credit-granting context behind the tool. While it doesn't enumerate every side effect, the security-sensitive behavior is transparently communicated and nothing contradicts the expected 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?

Four short sentences with no fluff. The purpose is front-loded, and each subsequent sentence adds a distinct fact: when to call, cost, and auth requirement. It doesn't restate schema details.

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?

An output schema is present, so return-value descriptions are unnneeded. The description covers the essential call sequence, cost, auth, and security rationale, while the input schema fully documents parameter formats. An agent has sufficient information to call this tool correctly.

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 coverage is 100%, so the baseline is 3. The description adds useful lifecycle context by stating that the invoice comes from purchase_credits and that npub ownership must be proven, which helps the agent understand the relationship between invoice_id, npub, and dpop_token beyond the raw schema text.

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 opens with a specific verb and resource: 'Check the payment status of a Lightning invoice.' This clearly distinguishes it from sibling check tools like authority_check_balance and authority_check_proof_status, and ties it to the purchase_credits flow.

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?

It explicitly tells the agent when to call the tool: 'Call after paying the invoice from purchase_credits.' It also adds cost and auth context ('Free — no credits required', 'Proof of npub ownership is required'), giving clear usage framing even without naming alternatives or explicit when-not-to-use cases.

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