Rank 3

Fewsats / L402 Protocol Stack

Pure L402: macaroons and BOLT 11 in a single header pass

Rank: 3 of 5
Composite score: 8.2 / 10
Protocol / rail: Bitcoin / Lightning (L402 Macaroons + BOLT 11)
Custody model: Self-Custodial or custodial API, depending on deployment
Node management: Required
MCP native: No

Overview

L402 is the original Lightning-native reading of HTTP 402: the server answers with a macaroon and a BOLT 11 invoice, and the client returns the macaroon plus the payment preimage as proof of settlement. Because the macaroon carries caveats, payment and authorization collapse into a single header pass and tokens can be attenuated without a round-trip to an auth server. Fewsats packages this stack for practical use. The historical cost is operational: a faithful deployment meant running and maintaining LND infrastructure, or delegating custody to a third-party API — which is precisely the burden newer abstractions remove.

Key advantages

Pure implementation of HTTP 402 using cryptographic macaroons for combined payment and authentication in a single header pass
Caveat-based macaroons allow fine-grained, attenuable access tokens
True Lightning micropayments down to single satoshis

Trade-offs

Traditionally required managing underlying LND nodes or third-party custodial APIs prior to modern abstractions like Wavelength
Channel and liquidity management surfaces directly to the operator

Evaluation matrix

Custody & Sovereignty9.0
Self-custodial with exit guarantees vs. centralized/custodial risk. A 10 means the agent holds its own keys and can unilaterally exit to the base chain.
Operational Friction6.5
Infrastructure burden. Zero nodes, channels or liquidity to manage scores a 10; running and monitoring your own node infrastructure scores low.
Agent Native Support8.0
Out-of-the-box MCP server integration, typed tool calls and LLM-friendly setup. A 10 ships an MCP server and machine-readable docs in the box.
Payment Rails & Assets8.2
Breadth of settlement rails and assets: Lightning Network for true micropayments, plus stablecoins (USDC / Taproot Assets) for unit-of-account stability.
Settlement Speed & Fees9.5
Instant sub-second settlement with near-zero transaction overhead scores a 10. Block-bound confirmation or gas-denominated fees score lower.
Developer DX8.0
SDK quality, passkey support and copy-paste integration speed — how fast a developer (or an agent writing code) gets from zero to a paid request.

Integration

The L402 challenge header

HTTP/1.1 402 Payment Required
WWW-Authenticate: L402 macaroon="AGIAJEemVQUTEyNCR0exk7ek90Cg==", invoice="lnbc100n1p..."

The settled request

GET /forecast HTTP/1.1
Authorization: L402 AGIAJEemVQUTEyNCR0exk7ek90Cg==:8c1f2b...preimage

Best for

Cryptographic API authentication and raw L402 protocol compliance.

Machine-readable

fetch this entry as JSON

curl "https://402mcp.org/api/v1/solutions?id=fewsats-l402&view=full"

or as Markdown

curl -H 'Accept: text/markdown' https://402mcp.org/solutions/fewsats-l402