---

name: nevermined-payments description: > Integrates Nevermined payment infrastructure into AI agents, MCP servers, Google A2A agents, and REST APIs. Handles x402 protocol, credit billing, payment plans, and SDK integration for TypeScript (@nevermined-io/payments) and Python (payments-py).

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

Variable	Required	Description
NVM_API_KEY	Yes	Your Nevermined API key (get it at nevermined.app → Settings → API Keys)
NVM_ENVIRONMENT	Yes	sandbox for testing, live for production
NVM_PLAN_ID	Yes	The plan ID from registration
NVM_AGENT_ID	Sometimes	Required for MCP servers and plans with multiple agents
BUILDER_ADDRESS	For registration	Wallet address to receive payments

.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:

Framework	Language	Reference	Key Import
Express.js	TypeScript/JS	references/express-integration.md	paymentMiddleware from @nevermined-io/payments/express
FastAPI	Python	references/fastapi-integration.md	PaymentMiddleware from payments_py.x402.fastapi
Strands Agent	Python	references/strands-integration.md	@requires_payment from payments_py.x402.strands
MCP Server	TypeScript	references/mcp-paywall.md	payments.mcp.start() / payments.mcp.registerTool()
Google A2A	TS / Python	references/a2a-integration.md	payments.a2a.start() / payments.a2a.buildPaymentAgentCard()
Any HTTP	Any	references/x402-protocol.md	Manual verify/settle via facilitator API
Client-side	TS / Python	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:

Header	Direction	Description
payment-signature	Client → Server	x402 access token
payment-required	Server → Client (402)	Base64-encoded JSON with plan requirements
payment-response	Server → Client (200)	Base64-encoded JSON settlement receipt

The payment-required payload structure:

{
  "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 for plan registration code.

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 for complete code.

// 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

Symptom	Cause	Fix
HTTP 402 returned	No payment-signature header or invalid/expired token	Generate a fresh token via getX402AccessToken
MCP error -32003	Payment Required — no token, invalid token, or insufficient credits	Check subscriber has purchased plan and has credits remaining
MCP error -32002	Server misconfiguration	Verify NVM_API_KEY, NVM_PLAN_ID, and NVM_AGENT_ID are set correctly
verification.isValid is false	Token expired, wrong plan, or insufficient credits	Re-order the plan or generate a new token
Credits not deducting	Settlement not called after request	Ensure you call settlePermissions after processing (middleware does this automatically)
payment-required header missing	Server not returning 402 properly	Use buildPaymentRequired() helper or framework middleware

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