Nevermined Payments Integration

Overview

Nevermined provides financial rails for AI agents — real-time monetization, access control, and payments. This skill gives you everything needed to:

• Protect API endpoints with the x402 payment protocol
• Charge per-request using credit-based billing
• Integrate with Express.js, FastAPI, Strands agents, MCP servers, or Google A2A agents
• Support subscriber-side flows (purchase plans, generate tokens, call protected APIs)
• Enable agent-to-agent payments via the Google A2A protocol

The x402 protocol uses HTTP 402 responses to advertise payment requirements. Clients acquire an access token and retry the request. The server verifies permissions, executes the workload, then settles (burns credits).

Quick Start Checklist

1. Get an API key at nevermined.app → Settings → API Keys
2. Install the SDK (

   npm install @nevermined-io/payments

   or

   pip install payments-py

   )
3. Register your agent and plan (via the App UI or programmatically — see

   references/payment-plans.md

   )
4. Add payment protection to your routes/tools (see framework-specific references below)
5. Test — call without token (expect 402), then with token (expect 200)

Environment Setup

NVM_API_KEY

NVM_ENVIRONMENT

sandbox

live

NVM_PLAN_ID

NVM_AGENT_ID

BUILDER_ADDRESS

.env

Template

# Required
NVM_API_KEY=your-api-key-here
NVM_ENVIRONMENT=sandbox
NVM_PLAN_ID=your-plan-id-here

# Required for MCP servers or multi-agent plans
NVM_AGENT_ID=your-agent-id-here

# Required for registration
BUILDER_ADDRESS=0xYourWalletAddress

Prerequisites

• TypeScript/Express.js: Node.js 18+. Your

  package.json

  must include

  "type": "module"

  for the

  @nevermined-io/payments/express

  subpath import to work.
• Python/FastAPI: Python 3.9+. Install with

  pip install payments-py[fastapi]

  — the

  [fastapi]

  extra is required for the middleware.

TypeScript

npm install @nevermined-io/payments

import { Payments } from '@nevermined-io/payments'

const payments = Payments.getInstance({
  nvmApiKey: process.env.NVM_API_KEY!,
  environment: 'sandbox'
})

Python

pip install payments-py

import os
from payments_py import Payments, PaymentOptions

payments = Payments.get_instance(
    PaymentOptions(
        nvm_api_key=os.environ["NVM_API_KEY"],
        environment="sandbox"
    )
)

Core Workflow (All Integrations)

Every Nevermined payment integration follows this 5-step pattern:

1. Client sends request without a payment token
2. Server returns 402 with

   payment-required

   header (base64-encoded JSON with plan info)
3. Client acquires x402 token via

   payments.x402.getX402AccessToken(planId, agentId)

4. Client retries with

   payment-signature

   header containing the token
5. Server verifies → executes → settles (burns credits), returns response with

   payment-response

   header

Framework Decision Tree

Choose the integration that matches your stack:

references/express-integration.md

paymentMiddleware

@nevermined-io/payments/express

references/fastapi-integration.md

PaymentMiddleware

payments_py.x402.fastapi

references/strands-integration.md

@requires_payment

payments_py.x402.strands

references/mcp-paywall.md

payments.mcp.start()

payments.mcp.registerTool()

references/a2a-integration.md

payments.a2a.start()

payments.a2a.buildPaymentAgentCard()

references/x402-protocol.md

references/client-integration.md

payments.x402.getX402AccessToken()

SDK Quick Reference

TypeScript (

@nevermined-io/payments

)

// Initialize
const payments = Payments.getInstance({ nvmApiKey, environment })

// Register agent + plan
const { agentId, planId } = await payments.agents.registerAgentAndPlan(
  agentMetadata, agentApi, planMetadata, priceConfig, creditsConfig
)

// Subscriber: order plan and get token
await payments.plans.orderPlan(planId)
const balance = await payments.plans.getPlanBalance(planId)
const { accessToken } = await payments.x402.getX402AccessToken(planId, agentId)

// Server: verify and settle
const verification = await payments.facilitator.verifyPermissions({
  paymentRequired, x402AccessToken: token, maxAmount: BigInt(credits)
})
const settlement = await payments.facilitator.settlePermissions({
  paymentRequired, x402AccessToken: token, maxAmount: BigInt(creditsUsed)
})

// Helpers
import { buildPaymentRequired } from '@nevermined-io/payments'
import { paymentMiddleware, X402_HEADERS } from '@nevermined-io/payments/express'

// MCP server
payments.mcp.registerTool(name, config, handler, { credits: 5n })
const { info, stop } = await payments.mcp.start({ port, agentId, serverName })

// A2A server
const agentCard = payments.a2a.buildPaymentAgentCard(baseCard, { paymentType, credits, planId, agentId })
const server = await payments.a2a.start({ port, basePath: '/a2a/', agentCard, executor })
// A2A client
const client = payments.a2a.getClient({ agentBaseUrl, agentId, planId })
await client.sendMessage("Hello", accessToken)

Python (

payments-py

)

# Initialize
payments = Payments.get_instance(PaymentOptions(nvm_api_key=key, environment="sandbox"))

# Register agent + plan
result = payments.agents.register_agent_and_plan(
    agent_metadata, agent_api, plan_metadata, price_config, credits_config
)

# Subscriber: order plan and get token
payments.plans.order_plan(plan_id)
balance = payments.plans.get_plan_balance(plan_id)
token_res = payments.x402.get_x402_access_token(plan_id, agent_id)

# Server: verify and settle
verification = payments.facilitator.verify_permissions(
    payment_required=pr, x402_access_token=token, max_amount=str(credits)
)
settlement = payments.facilitator.settle_permissions(
    payment_required=pr, x402_access_token=token, max_amount=str(credits_used)
)

# Helpers
from payments_py.x402.helpers import build_payment_required
from payments_py.x402.fastapi import PaymentMiddleware
from payments_py.x402.strands import requires_payment

# A2A server
from payments_py.a2a.agent_card import build_payment_agent_card
from payments_py.a2a.server import PaymentsA2AServer
agent_card = build_payment_agent_card(base_card, { ... })
server = PaymentsA2AServer.start(agent_card=agent_card, executor=executor, payments_service=payments, port=3005)
# A2A client
client = payments.a2a.get_client(agent_base_url=url, agent_id=agent_id, plan_id=plan_id)

x402 Payment Headers

All x402 v2 integrations use these three HTTP headers:

payment-signature

payment-required

payment-response

The

payment-required

{
  "x402Version": 2,
  "accepts": [{
    "scheme": "nvm:erc4337",
    "network": "eip155:84532",
    "planId": "<plan-id>",
    "extra": { "agentId": "<agent-id>" }
  }]
}

Payment Plan Types

Nevermined supports several plan types:

• Credits-based: prepaid balance, deducted per request (most common for APIs)
• Time-based: access for a fixed duration (e.g., 30 days unlimited)
• Pay-as-you-go (PAYG): settle in USDC per request, no credit balance
• Trial: free limited access, one-time claim per user
• Hybrid: combine credits with time expiry

See

references/payment-plans.md

Common Patterns

Express.js — Fixed credits per route

import { paymentMiddleware } from '@nevermined-io/payments/express'

app.use(paymentMiddleware(payments, {
  'POST /ask': { planId: PLAN_ID, credits: 1 },
  'POST /generate': { planId: PLAN_ID, credits: 5 }
}))

FastAPI — Fixed credits per route

from payments_py.x402.fastapi import PaymentMiddleware

app.add_middleware(
    PaymentMiddleware,
    payments=payments,
    routes={
        "POST /ask": {"plan_id": PLAN_ID, "credits": 1},
        "POST /generate": {"plan_id": PLAN_ID, "credits": 5}
    }
)

Express.js — Dynamic credits based on response

paymentMiddleware(payments, {
  'POST /generate': {
    planId: PLAN_ID,
    credits: (req, res) => {
      const tokens = res.locals.tokenCount || 100
      return Math.ceil(tokens / 100)
    }
  }
})

FastAPI — Dynamic credits based on request

async def calculate_credits(request: Request) -> int:
    body = await request.json()
    max_tokens = body.get("max_tokens", 100)
    return max(1, max_tokens // 100)

app.add_middleware(
    PaymentMiddleware,
    payments=payments,
    routes={"POST /generate": {"plan_id": PLAN_ID, "credits": calculate_credits}}
)

MCP Server — Register tool with paywall

payments.mcp.registerTool(
  "weather.today",
  { title: "Today's Weather", inputSchema: z.object({ city: z.string() }) },
  async (args, extra, context) => ({
    content: [{ type: "text", text: `Weather in ${args.city}: Sunny, 25C` }]
  }),
  { credits: 5n }
)

const { info, stop } = await payments.mcp.start({
  port: 3000,
  agentId: process.env.NVM_AGENT_ID!,
  serverName: "my-server"
})

Strands Agent — Decorator-based payment

from strands import Agent, tool
from payments_py.x402.strands import requires_payment

@tool(context=True)
@requires_payment(payments=payments, plan_id=PLAN_ID, credits=1)
def analyze_data(query: str, tool_context=None) -> dict:
    return {"status": "success", "content": [{"text": f"Analysis: {query}"}]}

agent = Agent(tools=[analyze_data])

Google A2A — Agent server with payment extension

TypeScript

const agentCard = payments.a2a.buildPaymentAgentCard(baseAgentCard, {
  paymentType: "dynamic",
  credits: 1,
  planId: process.env.NVM_PLAN_ID!,
  agentId: process.env.NVM_AGENT_ID!,
})

const server = await payments.a2a.start({
  port: 3005,
  basePath: '/a2a/',
  agentCard,
  executor: new MyExecutor(),
})

Python

from payments_py.a2a.agent_card import build_payment_agent_card
from payments_py.a2a.server import PaymentsA2AServer

agent_card = build_payment_agent_card(base_agent_card, {
    "paymentType": "dynamic",
    "credits": 1,
    "planId": os.environ["NVM_PLAN_ID"],
    "agentId": os.environ["NVM_AGENT_ID"],
})

server = PaymentsA2AServer.start(
    agent_card=agent_card,
    executor=MyExecutor(),
    payments_service=payments,
    port=3005,
    base_path="/a2a/",
)

Google A2A — Client sending a paid task

const client = payments.a2a.getClient({
  agentBaseUrl: 'http://localhost:3005/a2a/',
  agentId: AGENT_ID,
  planId: PLAN_ID,
})

const { accessToken } = await payments.x402.getX402AccessToken(PLAN_ID, AGENT_ID)
const response = await client.sendMessage("Analyze this data", accessToken)

Gathering Developer Information Upfront

When a developer asks you to integrate Nevermined payments, gather ALL required information in a single question before generating code. This avoids multiple back-and-forth interactions.

Ask the developer once for:

1. Framework: Express.js, FastAPI, MCP server, Strands agent, Google A2A, or generic HTTP?
2. Routes to protect: Which endpoints need payment protection and how many credits each? (e.g.,

   POST /chat = 1 credit, POST /generate = 5 credits

   )
3. Pricing model: Fixed credits per request, or dynamic pricing based on request/response parameters?
4. Nevermined API Key: Do they already have an

   NVM_API_KEY

   ? If not, direct them to nevermined.app → Settings → API Keys
5. Plan ID: Do they already have a

   NVM_PLAN_ID

   ? If not, do they need a registration script too?
6. Environment:

   sandbox

   (testing) or

   live

   (production)?

If they need plan registration, also ask:

7. Plan name and description: e.g., "Starter Plan — 100 API requests"
8. Pricing: How much in USDC? (e.g., 10 USDC for 100 credits)
9. Credits per plan: Total credits included (e.g., 100)
10. Builder wallet address (

    BUILDER_ADDRESS

    ): The wallet that receives payments

Example combined prompt to offer the developer:

I need to set up Nevermined payments. Here's my info:

• Framework: Express.js
• Routes: POST /chat (1 credit), POST /summarize (3 credits)
• I need a registration script too
• Plan: "Starter Plan", 100 credits for 10 USDC
• Environment: sandbox
• My API key is in the NVM_API_KEY env var
• My wallet: 0x1234...

With this information, generate both the registration script and the payment-protected server in a single response.

Agent and Plan Registration

Using the SDK (Recommended)

Register your agent and plan programmatically — see

references/payment-plans.md

// TypeScript
const { agentId, planId } = await payments.agents.registerAgentAndPlan(
  { name: 'My Agent', description: 'AI service', tags: ['ai'], dateCreated: new Date() },
  { endpoints: [{ POST: 'https://your-api.com/query' }] },
  { name: 'Starter Plan', description: '100 requests for $10', dateCreated: new Date() },
  payments.plans.getERC20PriceConfig(10_000_000n, USDC_ADDRESS, process.env.BUILDER_ADDRESS!),
  payments.plans.getFixedCreditsConfig(100n, 1n)
)

# Python
result = payments.agents.register_agent_and_plan(
    agent_metadata={'name': 'My Agent', 'description': 'AI service', 'tags': ['ai']},
    agent_api={'endpoints': [{'POST': 'https://your-api.com/query'}]},
    plan_metadata={'name': 'Starter Plan', 'description': '100 requests for $10'},
    price_config=get_erc20_price_config(10_000_000, USDC_ADDRESS, os.environ['BUILDER_ADDRESS']),
    credits_config=get_fixed_credits_config(100, 1)
)

Using the Nevermined App (No-Code)

1. Go to nevermined.app and sign in
2. Click "My agents" → register a new agent with metadata and endpoints
3. Create a payment plan: set pricing, credits, and duration
4. Link the plan to your agent and publish
5. Copy the

   agentId

   and

   planId

   for your

   .env

   file

Using the CLI

# 1. Install CLI
npm install -g @nevermined-io/cli

# 2. Configure (use sandbox for testing)
nvm config init --api-key "$NVM_API_KEY" --environment sandbox

# 3. Register agent and plan together
nvm agents register-agent-and-plan \
  --agent-metadata '{"name":"My Agent","description":"AI service"}' \
  --agent-api '{"endpoints":[{"POST":"https://your-api.com/query"}]}' \
  --plan-metadata '{"name":"Starter Plan","description":"100 requests"}' \
  --price-config '{"tokenAddress":"0x036CbD53842c5426634e7929541eC2318f3dCF7e","price":10000000,"amountOfCredits":100}' \
  --credits-config '{"minCreditsRequired":1,"minCreditsToCharge":1,"maxCreditsToCharge":10}'

# 4. List your plans
nvm plans get-plans

# 5. As a subscriber: order a plan and get an x402 token
nvm plans order-plan $PLAN_ID
nvm x402token get-x402-access-token $PLAN_ID --agent-id $AGENT_ID

# 6. Test against your running server
curl -X POST http://localhost:3000/chat \
  -H "Content-Type: application/json" \
  -H "payment-signature: $TOKEN" \
  -d '{"message": "Hello"}'

Troubleshooting

payment-signature

getX402AccessToken

-32003

-32002

NVM_API_KEY

NVM_PLAN_ID

NVM_AGENT_ID

verification.isValid

settlePermissions

payment-required

buildPaymentRequired()

Additional Resources

• Documentation: nevermined.ai/docs
• Nevermined App: nevermined.app — register agents, create plans, manage subscriptions
• MCP Search Server:

  https://docs.nevermined.app/mcp

  — search Nevermined docs from any MCP client
• Tutorials: github.com/nevermined-io/tutorials
• Discord: discord.com/invite/GZju2qScKq
• TypeScript SDK:

  @nevermined-io/payments

  on npm
• Python SDK:

  payments-py

  on PyPI