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

# Welcome

> Semantic is the payment infrastructure for AI agents. Trustless, P2P, and permissionless by design, so any agent can pay for data, compute, or capabilities, with private stablecoin settlement and no intermediary in the loop.

# Semantic

As AI agents graduate from simple tasks to sophisticated workflows — researching, reasoning, and acting autonomously across the internet — they hit a wall: **payments**.

Consider an agent tasked with generating a daily investment memo. It pulls market data from Kaiko, queries on-chain analytics from The Graph, runs sentiment analysis through an LLM, and compiles the output into a formatted report. Four providers, four API keys, four billing accounts, four sets of credentials to provision, rotate, and monitor. All before the agent has done anything useful. Add a fifth provider tomorrow and the whole stack needs re-plumbing.

This is the bottleneck. Every provider requires its own authentication, its own payment method, its own billing relationship. The agent can't just pay for what it needs and move on. It needs a human to pre-negotiate access at every layer.

## Agents need to pay for things

The use cases are already here. What's missing is the infrastructure to make them work.

<CardGroup cols={2}>
  <Card icon="database" title="Data">
    A research agent purchasing a premium dataset, a live feed, or a proprietary API mid-workflow.
  </Card>

  <Card icon="microchip" title="Compute">
    An orchestrator spinning up  inference on demand, paying per-token or per-job to the cheapest available provider.
  </Card>

  <Card icon="puzzle-piece" title="Capabilities">
    A coding agent spinning up a cloud sandbox to test its output. Paid instantly, no API key required.
  </Card>

  <Card icon="box" title="Goods">
    A procurement agent ordering physical inventory, booking logistics, or purchasing supplies.
  </Card>
</CardGroup>

## The infrastructure is missing

Traditional payment rails weren't designed for machines transacting with machines at the speed and scale that agents demand. What's needed is a fundamentally different approach.

<CardGroup cols={2}>
  <Card icon="shield-check" title="Human Oversight & Guardrails">
    Spend limits, approval flows, and kill switches. Agents operate within boundaries their owners define.
  </Card>

  <Card icon="fingerprint" title="Accountability & Authorization">
    Every payment is tied to an identity and a policy. Know which agent spent what, why, and whether it was authorized.
  </Card>

  <Card icon="route" title="End-to-End Traceability">
    Full audit trail from intent to settlement. Every request, authorization, and transfer is logged and verifiable.
  </Card>

  <Card icon="bolt" title="New Rails">
    Near-instant finality, low and predictable fees, privacy by default, and programmable transactions.
  </Card>
</CardGroup>

## How Semantic works

Semantic provides an [x402-compatible](https://www.x402.org) payment facilitator that makes agent payments as simple as an HTTP header.

We leverage **USD₮**, the world's most liquid stablecoin, on chains purpose-built for stablecoin transactions: [Plasma](https://plasma.to) and [Stable](https://stable.xyz). These chains deliver the speed, cost, and privacy properties that agent commerce requires, without the congestion and gas volatility of general-purpose L1s.

<AccordionGroup>
  <Accordion icon="globe" title="x402 Protocol">
    The x402 protocol extends HTTP with a native payment layer. When a resource requires payment, the server responds with `402 Payment Required` and the client settles automatically, no redirects, no checkout flows, no API keys.
  </Accordion>

  <Accordion icon="coins" title="USD₮0 on Plasma & Stable">
    USD₮0 supports EIP-3009 (`transferWithAuthorization`), enabling gasless, signature-based transfers. The payer signs, the facilitator submits, no gas tokens needed in the agent's wallet.
  </Accordion>

  <Accordion icon="bitcoin-sign" title="BTC Support (Coming Soon)">
    Native Bitcoin payments via Spark invoices, bringing the world's hardest asset into the agent economy alongside stablecoins.
  </Accordion>
</AccordionGroup>

## Get started

<CardGroup cols={3}>
  <Card icon="rocket" href="/client" title="Quick Setup">
    Get your first payment working in 5 minutes
  </Card>

  <Card icon="code" href="/endpoints" title="API Reference">
    Explore the facilitator endpoints
  </Card>

  <Card icon="map" href="/roadmap" title="Roadmap">
    See what's coming next
  </Card>
</CardGroup>

<Note>
  **Ready to build?** Start with the [Quick Setup](/client) to get your first agent payment working in under 5 minutes.
</Note>