VDM NexusDocs

SDK overview

Four MIT-licensed npm packages — sdk, x402, paywall, mcp. Pick the one that matches your role.

VDM Nexus ships four packages, each independently published and versioned. Most builders use one or two. None of them force a stack.

PackageRoleUse it when...
@vdm-nexus/sdkIdentityBuilding an agent that calls a Nexus endpoint via the prepaid flow. Same Ed25519 keypair handles signing requests and (optionally) paying via x402.
@vdm-nexus/x402Payment + verifierPay per inference call in USDC, or verify a receipt someone else produced. Includes the five-check verifyReceipt used by everyone else.
@vdm-nexus/paywallMonetize your own APIYou run an Express, Hono, or Next.js handler and want to charge per call with a signed receipt of the output.
@vdm-nexus/mcpClaude Desktop / CursorDrop signed inference into a Claude Desktop or Cursor workflow without writing a custom agent.

All four are MIT, all four live in the monorepo under packages/.

How they fit

  Agent (your code)            Nexus / any SIR endpoint
  ─────────────────            ───────────────────────────
  @vdm-nexus/sdk               @vdm-nexus/paywall
      │                              │
      │   signed request             │   signed receipt
      └──────────────►───────────────┘
                                     │
                                     ▼
                            @vdm-nexus/x402.verifyReceipt
                                     │
                              (5 checks: hashes,
                               operator signature,
                               on-chain tx,
                               payer match,
                               recipient match)

  Or skip the custom agent and use MCP:

  Claude Desktop / Cursor
      │
      │   config: @vdm-nexus/mcp
      └──────────────►   Nexus

The protocol is the product — @vdm-nexus/x402's verifyReceipt and the SIR v2 spec are designed so anyone can write their own client or verifier and stay interoperable.

Three promises that don't change

  • MIT-licensed forever. Every package, every release. Fork it, embed it, ship it.
  • Tiny runtime dependency surface. @vdm-nexus/sdk has two runtime deps (tweetnacl, bs58). The whole chain is auditable in an afternoon. Adding a third needs justification.
  • The spec is public. SIR v2 is at docs.vdmnexus.com/docs/spec/sir-v2. Any package — ours or someone else's — can produce or verify receipts and stay compatible.

Picking one

If you want a one-liner decision:

  • Just want signed inference from Claude Desktop? → @vdm-nexus/mcp, paste a JSON block, done.
  • Building an agent in TypeScript / Node? → @vdm-nexus/sdk for prepaid, or @vdm-nexus/x402 if you want pay-per-call.
  • You run an AI API and want users to pay per call? → @vdm-nexus/paywall.
  • You're an auditor, CI bot, or third-party verifier? → @vdm-nexus/x402's verifyReceipt. No agent secret required.

See it work

Every package above runs a real call in the hosted playground. No install, no USDC needed — the operator's wallet pays. Useful for verifying that the endpoint, the receipt shape, and the verifier all match what you'd see from your own code.

Where to next

Skim the reference for whichever package matches your role. Each one has install instructions, an end-to-end snippet, and a "things this SDK doesn't do" section so you know the edges:

Agent-git primitives

Three discrete products that turn the signed-inference rail into a workflow teams can adopt — provenance, payment-gated merges, and signed release tags. Shipping next, after mainnet.

@vdm-nexus/sdk reference

API reference for the lean prepaid-flow SDK.

On this page

How they fitThree promises that don't changePicking oneSee it workWhere to next