Nevermined Payments

Nevermined Payments Integration

> Skill version: 0.3.3 | Last updated: 2026-05-06 > > Verified against @nevermined-io/payments@1.3.3 and payments-py@1.5.0.

Overview

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

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).

Nevermined API Key Prerequisite

A Nevermined API Key (NVM_API_KEY) is required for ALL interactions with the Nevermined platform — SDK initialization, REST API calls, CLI usage, and agent registration. Without it, nothing works.

If the developer already has a key, they can skip this section and set it as an environment variable:

export NVM_API_KEY="sandbox:your-api-key"

If the developer does NOT have a key, guide them through these steps:

1. Open nevermined.app and sign in 2. Navigate to Settings > Global NVM API Keys 3. Click + New API Key 4. Enter a descriptive name, select the required permissions, and click Generate API Key 5. Click Copy Key and store it securely as an environment variable (NVM_API_KEY)

The key format is : — for example sandbox:eyJhbGci... or live:eyJhbGci....

Full documentation: Get Your API Key

> IMPORTANT for AI agents: If you are generating code that requires NVM_API_KEY and the developer has not provided one, you MUST tell them to create one first by following the steps above or visiting nevermined.app. Never generate placeholder keys that look real. Always use sandbox:your-api-key as the placeholder value.

Quick Start Checklist

1. Get an API key — see Nevermined API Key Prerequisite above 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 — see Get Your API Key | | 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=sandbox:your-api-key
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

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, { delegationConfig }) — requires a delegation (either an existing delegationId or spendingLimitCents + durationSecs to auto-create one) 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() with delegationConfig |

SDK Quick Reference

TypeScript (@nevermined-io/payments)

// Initialize
const payments = Payments.getInstance({ nvmApiKey, environment })
// Build price + credits configs (pick one helper per axis)
const priceConfig =
  payments.plans.getERC20PriceConfig(10_000_000n, USDC_ADDRESS, builderAddress)
  // or getEURCPriceConfig / getNativeTokenPriceConfig / getFreePriceConfig
  // or getFiatPriceConfig(amount, builderAddress, 'USD') for Stripe/Braintree
  // or await getPayAsYouGoPriceConfig(amount, builderAddress, tokenAddress?)
const creditsConfig =
  payments.plans.getFixedCreditsConfig(100n, 1n)
  // or getDynamicCreditsConfig / getExpirableDurationConfig
  // or getPayAsYouGoCreditsConfig() for PAYG plans
// 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 planBalance = await payments.plans.getPlanBalance(planId)
console.log(Credits remaining: ${planBalance.balance})  // PlanBalance.balance is bigint
const { accessToken } = await payments.x402.getX402AccessToken(planId, agentId, {
  delegationConfig: { spendingLimitCents: 100, durationSecs: 3600 }
})
// 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)

from payments_py.x402 import DelegationConfig, X402TokenOptions
Initialize
payments = Payments.get_instance(PaymentOptions(nvm_api_key=key, environment="sandbox"))
Build price + credits configs (helpers exist on payments.plans and as module funcs)
price_config = payments.plans.get_erc20_price_config(10_000_000, USDC_ADDRESS, builder_address)
or get_eurc_price_config / get_native_token_price_config / get_free_price_config
or get_fiat_price_config(amount, builder_address, "USD") for Stripe/Braintree
or payments.plans.get_pay_as_you_go_price_config(...)  (sync; uses cached contract address)
credits_config = payments.plans.get_fixed_credits_config(100, 1)
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)
plan_balance = payments.plans.get_plan_balance(plan_id)
print(f"Credits remaining: {plan_balance.balance}")  # PlanBalance.balance is int
token_res = payments.x402.get_x402_access_token(
    plan_id, agent_id,
    token_options=X402TokenOptions(
        delegation_config=DelegationConfig(spending_limit_cents=100, duration_secs=3600)
    )
)
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": "",
    "extra": { "agentId": "" }
  }]
}

Supported x402 schemes

| Scheme | Network field | Settlement | |---|---|---| | nvm:erc4337 | CAIP-2 chain ID (e.g. eip155:84532 Base Sepolia, eip155:8453 Base Mainnet) | Crypto stablecoins (USDC / EURC) via account-abstraction delegation | | nvm:card-delegation | Fiat provider (stripe or braintree) | Card-on-file via Stripe or Braintree delegation |

The SDK auto-resolves the scheme from the plan's priceConfig metadata. You only need to pass scheme explicitly if you want to override it.

Payment Plan Types

Nevermined supports several plan types:

Each plan can be priced in crypto (getERC20PriceConfig, getEURCPriceConfig, getNativeTokenPriceConfig) or fiat (getFiatPriceConfig — Stripe/Braintree). The selected price helper determines the x402 scheme used at runtime.

For fiat plans, the active provider is selected per plan via the fiatPaymentProvider metadata field ('stripe' or 'braintree'). Sellers using Braintree must connect a Braintree merchant account with at least one child merchant account in the plan's currency — see braintree-onboarding for the seller-side setup and card-enrollment for the buyer-side flow.

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, {
  delegationConfig: { spendingLimitCents: 100, durationSecs: 3600 }
})
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 Get Your API Key 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 + agentDefinitionUrl are both optional in AgentAPIAttributes.
  // Provide endpoints only when you want the Nevermined platform to enforce
  // route-level Additional Security on top of your library middleware.
  { 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
from payments_py.plans import get_erc20_price_config, get_fixed_credits_config
(or use the methods on payments.plans.* — both are equivalent)
result = payments.agents.register_agent_and_plan(
    agent_metadata={'name': 'My Agent', 'description': 'AI service', 'tags': ['ai']},
    # agent_api is required, but its endpoints and agent_definition_url
    # fields are both optional. Omit them for an open agent (no platform-side
    # route enforcement); include endpoints for Additional Security.
    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 "$NVM_API_KEY" --environment sandbox
3. Build the helper-shaped configs and register
   The --price-config / --credits-config flags expect the JSON shape
   produced by Plans.getERC20PriceConfig and Plans.getFixedCreditsConfig —
   the helper subcommands below emit exactly that shape with --format json.
PRICE=$(nvm plans get-erc20-price-config \
  --amount 10000000 \
  --token-address 0x036CbD53842c5426634e7929541eC2318f3dCF7e \
  --receiver $BUILDER_ADDRESS \
  --format json)
CREDITS=$(nvm plans get-fixed-credits-config \
  --credits-granted 100 \
  --credits-per-request 1 \
  --format json)
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 "$PRICE" \
  --credits-config "$CREDITS"
4. List your plans
nvm plans get-plans
5. As a subscriber: order a plan and get an x402 token
   For fiat plans, pass --payment-type fiat (defaults to crypto).
nvm plans order-plan $PLAN_ID
nvm x402token get-x402-access-token $PLAN_ID \
  --agent-id $AGENT_ID \
  --spending-limit-cents 10000 \
  --delegation-duration-secs 604800
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 with delegationConfig | | 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

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"
    )
)

| Symptom | Cause | Fix | |---|---|---| | HTTP 402 returned | No payment-signature header or invalid/expired token | Generate a fresh token via getX402AccessToken with delegationConfig | | 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 |