> ## Documentation Index
> Fetch the complete documentation index at: https://docs.nevermined.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Technical Specifications

> Formal specifications for Nevermined protocol, extensions, and integration standards

This section contains the **technical specifications** that define how Nevermined protocol and extensions work. These documents are intended for developers building integrations, protocol implementers, and anyone who needs to understand the precise behavior of Nevermined systems.

## Purpose

Specifications in this section:

* **Define normative behavior** using precise, unambiguous language
* **Follow RFC 2119 conventions** for requirement levels (MUST, SHOULD, MAY)
* **Include data structures** with exact field definitions and types
* **Document protocol flows** with sequence diagrams and state transitions
* **Specify error handling** and edge cases

## Audience

These specifications are written for:

* **Protocol implementers** building x402 facilitators or clients
* **SDK developers** creating libraries that interact with Nevermined
* **Integration engineers** connecting existing systems to Nevermined
* **Security auditors** reviewing protocol designs

## Relationship to Other Documentation

| Documentation Type     | Purpose                                    |
| ---------------------- | ------------------------------------------ |
| **Getting Started**    | Quickstart guides and tutorials            |
| **Use Cases**          | Business scenarios and solution patterns   |
| **Integration Guides** | Step-by-step implementation instructions   |
| **API Reference**      | SDK methods and REST endpoints             |
| **Specifications**     | Formal protocol definitions (this section) |

Specifications are the **source of truth** for protocol behavior. Other documentation may simplify or summarize, but specifications define what implementations MUST do.

## Conventions

### Requirement Levels

This documentation uses RFC 2119 terminology:

* **MUST** / **REQUIRED** / **SHALL** — absolute requirement
* **MUST NOT** / **SHALL NOT** — absolute prohibition
* **SHOULD** / **RECOMMENDED** — there may be valid reasons to ignore, but implications must be understood
* **SHOULD NOT** / **NOT RECOMMENDED** — there may be valid reasons to do this, but implications must be understood
* **MAY** / **OPTIONAL** — truly optional behavior

### Data Types

* JSON structures use TypeScript-style type annotations
* Hexadecimal values are prefixed with `0x`
* Base64 encoding uses standard alphabet with `=` padding
* Timestamps use ISO 8601 format unless otherwise specified

## Available Specifications

<CardGroup cols={1}>
  <Card title="x402 Smart Accounts Extension" icon="key" href="/docs/specs/x402-smart-accounts">
    Extends x402 with ERC-4337 smart accounts, session keys, and programmable smart contract settlement
  </Card>

  <Card title="x402 Card Delegation Extension" icon="credit-card" href="/docs/specs/x402-card-delegation">
    Extends x402 with credit/debit card delegation via Stripe for fiat-based payment settlement
  </Card>
</CardGroup>

## Contributing

Specifications evolve based on implementation experience and community feedback. If you identify ambiguities, errors, or improvements, please open an issue in the [Nevermined GitHub repository](https://github.com/nevermined-io).