Decode any BOLT11 invoice to view its amount, description, expiry, and destination without paying. Works without an API key or registration.
Decode a BOLT11 invoice without paying it. Returns amount, description, expiry, and destination. No API key required — works before registering.
| Name | Required | Description | Default |
|---|---|---|---|
| bolt11 | Yes | BOLT11 invoice string to decode |
Changes observed during successful MCP inspections.
v1.2.9Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the burden. It discloses that the tool is non-mutating ('without paying it') and that it works pre-registration, which is useful. However, it doesn't mention error behavior for invalid invoices, whether the invoice is validated, or any rate-limit implications. The core safety trait (no payment) is disclosed, but other behavioral details are missing.
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 sentences with no wasted words. The primary action and key safety qualifier ('without paying it') are front-loaded, and the no-API-key note is a valuable addition in the second sentence.
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 single-parameter read-only decode tool, the description is nearly complete. It states what it returns (amount, description, expiry, destination), which is helpful since there is no output schema. It could mention invalid-input behavior, but the tool is simple enough that this is a minor gap.
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 the bolt11 parameter. The description adds that the parameter is a BOLT11 invoice string, which is redundant with the schema. It doesn't add format details, examples, or constraints beyond what the schema provides. Baseline 3 is appropriate.
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 verb 'Decode' and the resource 'BOLT11 invoice', and explicitly notes it does not pay the invoice. This distinguishes it from payment-related siblings like pay_invoice and pay_l402_api, and from create_invoice which creates rather than decodes.
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 implies when to use it: when you need invoice details without paying. It also notes no API key is required and works before registering, which is a clear usage context. It doesn't explicitly name alternatives or exclusions, but the 'without paying it' phrasing effectively distinguishes it from payment tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.