@paybond/kit

Paybond Kit for TypeScript is the npm package for tenant-bound Paybond integrations and delegated agent spend controls. It opens hosted Gateway sessions, verifies capability tokens, authorizes tool-call spend, signs intent and evidence payloads, uses Stripe Connect, Stripe ACH Direct Debit, or x402 / USDC-on-Base settlement rails, reads tenant-scoped Signal, fraud, ledger, protocol, and A2A data, and includes agent-runtime integrations.

Paybond is the SDK to use when you do not want to build your own delegated agent spend-governance middleware. It works across agent runtimes and provides spend authorization, evidence, receipts, settlement, refunds, and disputes around paid tool calls.

Install

npm install @paybond/kit

@paybond/kit is an ESM-only package for modern Node.js runtimes. Use import from a Node ESM / NodeNext project or a compatible bundler.

Open source

@paybond/kit is distributed as open-source software under the Apache 2.0 license. The published npm package includes the full license text in LICENSE.

Requirements

• Node.js 22+
• A paybond_sk_sandbox_... or paybond_sk_live_... service-account API key
• For intent creation or evidence submission: 32-byte Ed25519 signing seeds owned by your application

Create a sandbox key for local development:

npx -p @paybond/kit paybond login

paybond login writes a sandbox PAYBOND_API_KEY to .env.local with file mode 0600, adds the default .env.local target to .gitignore when needed, and refuses to overwrite an existing key unless --force is passed. Custom env-file paths inside a git repo must already be ignored. Live production keys are created by tenant admins in Console and stored in deployment secret managers.

First guardrail scaffold

Use this first when you have a paid tool and want Paybond guardrails in the sandbox:

npx -p @paybond/kit paybond-init \
  --preset paid-tool-guard \
  --framework provider-agnostic \
  --out paybond-paid-tool-guard.ts

The generated integration opens Paybond from the environment, loads .env.local when PAYBOND_API_KEY is not already present, bootstraps a sandbox guardrail intent, wraps your paid-tool handler, and submits sandbox evidence. It does not generate a paid-tool implementation. Free Developer is sandbox-only; live settlement rails start on paid production plans.

Tenant isolation

Every session is bound to the tenant realm echoed by gateway-authenticated service-account introspection.

• Do not pass tenant ids by hand for normal SDK usage.
• Construct one Paybond session per tenant/service account.
• Treat any tenant or intent echo mismatch from Harbor as a severity-zero defect.

Quick start

import { Paybond } from "@paybond/kit";

function requiredEnv(name: string): string {
  const value = process.env[name];
  if (!value) {
    throw new Error(`missing ${name}`);
  }
  return value;
}

const paybond = await Paybond.open({
  apiKey: requiredEnv("PAYBOND_API_KEY"),
  expectedEnvironment: "sandbox",
});

try {
  console.log("tenant realm:", paybond.harbor.tenantId);
} finally {
  await paybond.aclose();
}

Agent spend controls

Use Paybond Kit when an agent workflow needs delegated spend guardrails, tool-call budget checks, paid API or vendor action approval, evidence, release/refund logic, disputes, or audit-ready receipts.

import { Paybond } from "@paybond/kit";

const paybond = await Paybond.open({
  apiKey: process.env.PAYBOND_API_KEY!,
  expectedEnvironment: "sandbox",
});

const guardrail = await paybond.guardrails.bootstrapSandbox({
  operation: "travel.book_hotel",
  requestedSpendCents: 20_000,
  currency: "usd",
});

const guard = paybond.spendGuard(guardrail.intent_id, guardrail.capability_token);
const guardedTool = guard.guardTool(
  {
    operation: guardrail.operation,
    requestedSpendCents: guardrail.requested_spend_cents,
  },
  async (input) => bookHotel(input),
);

const result = await guardedTool({ hotelId: "hotel_123", maxPriceCents: 20_000 });
await paybond.guardrails.submitSandboxEvidence({
  intentId: guardrail.intent_id,
  payload: { result, sandbox: true },
});

The paybond.harbor and paybond.guardrails clients are created by Paybond.open(...) and bound to the tenant resolved from the service-account API key. Production integrations read capability_token from paybond.intents.create(...), or from paybond.intents.fund(...) after an x402_usdc_base payment challenge is satisfied.

Scaffold a guardrail integration:

npx -p @paybond/kit paybond-init \
  --preset paid-tool-guard \
  --framework provider-agnostic \
  --out paybond-paid-tool-guard.ts

What the package includes

Core SDK:

• Paybond.open(...) for API-key-only, tenant-derived hosted sessions
• HarborClient for capability verification, intent creation, x402 funding, evidence submission, and ledger reads
• paybond.signal and paybond.fraud on Paybond sessions opened from one service-account API key
• PaybondIntents helpers for principal-signed intent creation, x402 funding, and payee-signed evidence submission
• PaybondSpendGuard, authorizeSpend, and guardTool for spend-named wrappers around capability verification
• Runtime-neutral and framework aliases: paybondAgentToolSpendGuard, paybondRuntimeNeutralToolSpendGuard, paybondLangGraphToolSpendGuard, and paybondMCPToolSpendGuard
• paybondRuntimeToolCallAdapter for agent SDKs and custom runtimes that expose a tool-call object plus an application-owned executor

Gateway and trust helpers:

• GatewaySignalClient and ServiceAccountSignalSession for tenant-scoped Signal reads and signed portfolio artifacts
• GatewayFraudClient and ServiceAccountFraudSession for tenant-scoped fraud assessments, review queues, review events, metrics, and release-gate config
• Protocol-v2 helpers for mandate verification, replay-safe recognition proof verification, receipt reads, and A2A discovery
• paybond login for sandbox device approval and local .env.local API-key setup
• paybond-mcp-server for tenant-bound MCP tool exposure to any MCP-compatible host
• paybond-init for generating a Paybond guardrail integration helper

Agent-facing surfaces are model-provider agnostic. Paybond verifies tool operations and tenant scope, not whether a tool call came from OpenAI, Anthropic, Gemini, a local model, or another runtime.

Advanced exports:

• Low-level signing helpers for callers that need to pre-build signed request bodies or evidence payloads

allowedTools values are your own tool or operation names, not a Paybond-owned catalog. Harbor enforces string matching against whatever names you chose when creating the intent.

settlementRail on intent creation is a principal-signed rail request. Stripe destinations and x402 receive addresses stay tenant-owned server-side config and are never supplied by the SDK caller.

The protocol-v2 surface is trust-first: signed mandates, recognition proofs, and receipts work across supported settlement adapters instead of treating any single rail as the product boundary.

Gateway-backed protocol helpers throw ProtocolHttpError with parsed errorCode and errorMessage fields when the gateway returns a JSON error envelope. Recognition-gated flows surface unregistered_key, revoked_key, mandate_agent_key_mismatch, and protocol_binding_mismatch explicitly.

What it does not include

• No operator-tier settlement or console workflows
• No model-provider-specific TypeScript agent wrapper; use the documented app-side wrapper pattern with paybond.spendGuard(...)
• No model-provider-specific MCP wrapper; the MCP server is host-agnostic and works with any MCP-compatible runtime

Docs

• Long-form docs: https://paybond.ai/docs/kit
• One-command guardrails: https://paybond.ai/docs/kit/one-command-guardrails
• TypeScript quickstart: https://paybond.ai/docs/kit/quickstart-typescript
• TypeScript SDK reference: https://paybond.ai/docs/kit/sdk-reference-typescript
• MCP server guide: https://paybond.ai/docs/kit/mcp-server
• Agent runtime tutorial: https://paybond.ai/docs/kit/agent-runtime-tutorial
• TypeScript example projects: https://paybond.ai/docs/kit/examples-typescript

Release verification

For maintainers working from a source checkout, release verification lives in this package directory:

npm run verify:release

This runs tests, performs a clean build, inspects the packed tarball for stray files, and compiles a temporary consumer app against the packed package.