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A paid API integration only works if agents can find it without a human pointing the way. Today the de facto convention is the llms.txt file: a static llms.txt at the root of your docs site that lists, in plain Markdown, the resources you want LLMs to know about. Exa proved this works in production. Their llms.txt has a single line under ## Integrations pointing to nevermined.md, and that’s it — every agent that reads their docs index now knows the Nevermined integration exists, what it costs, and how to invoke it. This page covers how to do the same for your service.

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The two files you need

1

A line in your llms.txt

Add an ## Integrations section (if you don’t have one) and a single line linking to your Nevermined integration page. That’s the entry point — every LLM-aware crawler that reads your llms.txt will follow this link.
2

A nevermined.md page on your docs site

A short Markdown page describing how an agent should pay for and use your service. Structure it the same way Exa does so agents that have already seen one integration page can navigate yours without surprises.

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What goes in nevermined.md

Six sections, in this order:
SectionWhy it’s there
IntroOne sentence: what your service does, what the integration enables.
Buy a keyThe endpoint URL + the payment-signature header. The “API surface” of the integration.
What $X buysPricing table mapping the plan price to concrete units in your product (e.g. “1000 searches”, “10,000 documents”).
Sample requestA complete, copy-pasteable TypeScript snippet. The reference for any agent that needs to generate code.
Parameters you get from NeverminedPlan ID, scheme (nvm:card-delegation), spending limit, network — the concrete values an agent needs to substitute in.
When the key runs outThe HTTP 402 response shape (status code, error tag, message). Agents must key off tag: "NO_MORE_CREDITS", not your human-readable error string.
ReferencesLinks to your full API docs, Nevermined docs, x402 spec.

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Copy-paste template

The same templates ship inside the web-search-paid-api-ts tutorial under src/llms-txt-template/. Pull them from there if you’d rather grab the raw files.

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llms.txt (root of your docs site)

# {{SERVICE_NAME}}

> {{ONE_SENTENCE_DESCRIPTION}}. AI agents can buy access autonomously via Nevermined — no human onboarding required.

## Docs

- [API reference]({{API_REFERENCE_URL}}): every endpoint, with request and response shapes.
- [Getting started]({{QUICKSTART_URL}}): the human-facing onboarding path.

## Integrations

- [Nevermined]({{NEVERMINED_INTEGRATION_MD_URL}}): autonomous agent payments. A {{PRICE_USD}} purchase provisions or tops up a {{SERVICE_NAME}} API key with {{QUOTA_PER_PURCHASE}} requests. One endpoint, one card charge, no metering changes on the provider side.

## Optional

- [Pricing]({{PRICING_URL}})
- [Status page]({{STATUS_URL}})

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nevermined.md (next to your other integration docs)

# Nevermined

Autonomous agent payments for {{SERVICE_NAME}} via Nevermined x402 card delegation. A {{PRICE_USD}} purchase provisions or tops up a {{SERVICE_NAME}} API key with {{QUOTA_PER_PURCHASE}} requests.

## Buy a key

```
POST {{PURCHASE_ENDPOINT_URL}}
payment-signature: <x402-token>
```

Pay with a credit card enrolled in [Nevermined](https://nevermined.app). One successful POST = one card charge of {{PRICE_USD}}. The response contains a {{SERVICE_NAME}} API key you can use against the regular endpoints.

## What {{PRICE_USD}} buys

| Endpoint | Cost per call | Calls per purchase |
| --- | --- | --- |
| `{{ENDPOINT_A_PATH}}` | 1 request | {{QUOTA_PER_PURCHASE}} |
| `{{ENDPOINT_B_PATH}}` | {{ENDPOINT_B_COST}} requests | {{ENDPOINT_B_CALLS}} |
| `{{ENDPOINT_C_PATH}}` | {{ENDPOINT_C_COST}} requests | {{ENDPOINT_C_CALLS}} |

Provider-side metering. Independent of any Nevermined credit balance.

## Sample request

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

const PLAN_ID = '{{NEVERMINED_PLAN_ID}}'

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

// 1. Mint an x402 token scoped to an enrolled card.
const { accessToken } = await payments.x402.getX402AccessToken(PLAN_ID, undefined, {
  scheme: 'nvm:card-delegation',
  delegationConfig: {
    providerPaymentMethodId: 'pm_...',     // Stripe payment method enrolled in Nevermined
    spendingLimitCents: {{PRICE_CENTS}},  // >= the plan price
    durationSecs: 3600,
  },
})

// 2. Exchange the token for (or top up) an API key.
const res = await fetch('{{PURCHASE_ENDPOINT_URL}}', {
  method: 'POST',
  headers: { 'payment-signature': accessToken },
})
const { apiKey } = await res.json()

// 3. Use the key against the normal {{SERVICE_NAME}} endpoints.
const search = await fetch('{{REGULAR_ENDPOINT_URL}}', {
  method: 'POST',
  headers: { 'x-api-key': apiKey, 'content-type': 'application/json' },
  body: JSON.stringify({ query: 'agentic payments' }),
})
```

## Parameters you get from Nevermined

| Field | Value | Where to find it |
| --- | --- | --- |
| Plan ID | `{{NEVERMINED_PLAN_ID}}` | Listed above; or look up your plan on https://nevermined.app |
| Scheme | `nvm:card-delegation` | Fixed for this integration |
| Spending limit | At least `{{PRICE_CENTS}}` cents | Must cover one purchase |
| Network / environment | `live` (or `sandbox` for testing) | Match the environment the plan was created in |

## When the key runs out

When the API key's quota is exhausted, regular endpoints return HTTP 402 with:

```json
{
  "tag": "NO_MORE_CREDITS",
  "error": "API key has no remaining requests. Top up by calling {{PURCHASE_ENDPOINT_URL}}."
}
```

To top up, call `POST {{PURCHASE_ENDPOINT_URL}}` again with a fresh x402 token. The same card is charged, the same API key is returned with {{QUOTA_PER_PURCHASE}} additional requests credited.

Agents should key off `tag: "NO_MORE_CREDITS"`, not the human-readable `error` string — the wording may vary between providers, the tag is the stable contract.

## References

- {{SERVICE_NAME}} API docs: {{API_REFERENCE_URL}}
- Nevermined docs: https://docs.nevermined.io
- x402 specification: https://github.com/coinbase/x402
- Nevermined x402 module (TypeScript): https://docs.nevermined.io/docs/api-reference/typescript/x402

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Where to host the files

FileHosting locationWhy
llms.txtRoot of your docs site, e.g. https://yourservice.example/docs/llms.txtThe llms.txt convention says “at the root”. Crawlers look there first.
nevermined.mdNext to your other integration docs, e.g. https://yourservice.example/docs/integrations/nevermined.mdURL must be stable — the llms.txt entry references it by absolute URL.
If your docs site doesn’t already publish .md mirrors next to your HTML pages, you’ll need to add that. Mintlify-based sites get it automatically; for other doc tools the easiest path is dropping the file in public/ or whatever your static-asset folder is called.

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Test it before agents see it

1

Verify the file is reachable

curl https://yourservice.example/docs/llms.txt and curl https://yourservice.example/docs/integrations/nevermined.md should both return 200 with the expected content. No JavaScript redirects, no auth walls.
2

Validate the sample request

Run the TypeScript snippet in your nevermined.md against your real endpoint, using a sandbox plan. If your own copy-paste doesn’t work, no agent’s will either.
3

Have an LLM follow the chain

Paste your llms.txt URL into Claude, ChatGPT, or any agent that supports web fetching, and ask: “I want to use {{SERVICE_NAME}}. Read the llms.txt and explain how an agent would pay for and use this service.” The summary should match what you actually built — if it doesn’t, your nevermined.md is ambiguous.

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Known agent rakes

Tips collected from running real agents against real integration pages. This list will grow as we validate more agents against the pattern.
This section will be populated after the multi-agent validation pass that follows nevermined-io/nvm-monorepo#1684. For now, the test it before agents see it checklist above covers the basics.