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

# Facilitators

> Settlement services that verify and submit x402 agent payments on Stable so you do not run your own infrastructure.

A facilitator verifies a signed x402 payment and submits the on-chain call that settles it in USDT0 on Stable. Using a hosted facilitator means you do not run settlement infrastructure or manage gas tokens. For the rail-level context, see [Agent settlement](/en/explanation/agent-settlement).

## Overview table

| **Provider**                                    | **Category**     | **Docs / Get Started**                                                                                                                       | **Notes**                                                                                                       |
| :---------------------------------------------- | :--------------- | :------------------------------------------------------------------------------------------------------------------------------------------- | :-------------------------------------------------------------------------------------------------------------- |
| [**Semantic Pay**](https://x402.semanticpay.io) | x402 facilitator | [https://docs.semanticpay.io/supported-chains#stable](https://docs.semanticpay.io/supported-chains#stable)                                   | Public x402 facilitator for Stable; verifies and settles USDT0 payments via ERC-3009                            |
| [**Heurist**](https://facilitator.heurist.xyz)  | x402 facilitator | [https://docs.heurist.ai/x402-products/facilitator#supported-networks](https://docs.heurist.ai/x402-products/facilitator#supported-networks) | Multi-chain x402 facilitator supporting Stable; high-throughput verification and settlement with OFAC screening |

## Semantic Pay

Payment infrastructure for AI agents: trustless, P2P, and permissionless. Semantic Pay operates as an x402-compatible payment facilitator on Stable, settling USDT0 payments via ERC-3009 (`transferWithAuthorization`). Agents do not need a separate gas token in their wallets.

Developers integrating x402 on Stable point their middleware to `https://x402.semanticpay.io`. No custom settlement infrastructure is required.

**Capabilities**

* Payment payload verification (`/verify`) and on-chain settlement (`/settle`) via USDT0
* Gasless transfers using ERC-3009 `transferWithAuthorization`
* Spend limits, approval flows, and kill switches for agent oversight
* End-to-end traceability with full audit logging from intent through settlement
* Event callbacks for real-time payment lifecycle updates

**Facilitator endpoint:** `https://x402.semanticpay.io`

**Docs:** [https://docs.semanticpay.io/supported-chains#stable](https://docs.semanticpay.io/supported-chains#stable)

## Heurist

Heurist operates a multi-chain x402 facilitator that supports Stable alongside Base, Base Sepolia, and X Layer. It targets high-frequency agent workloads with throughput tuned for thousands of payment verifications and settlements per second.

Point your middleware at `https://facilitator.heurist.xyz`. No API key is required to get started.

**Capabilities**

* Payment verification and on-chain settlement across multiple networks from one endpoint
* Throughput sized for high-frequency agent traffic
* Automatic OFAC screening of sender addresses
* Real-time observability over verification and settlement activity

**Facilitator endpoint:** `https://facilitator.heurist.xyz`

**Docs:** [https://docs.heurist.ai/x402-products/facilitator#supported-networks](https://docs.heurist.ai/x402-products/facilitator#supported-networks)

## How to choose

* Use a hosted facilitator (Semantic Pay or Heurist) to start fast. No infrastructure to run, no gas tokens to manage.
* Pick by what matters most for your workload: Semantic Pay if you want Stable-native tooling with lifecycle callbacks and agent oversight controls; Heurist if you need a single endpoint that spans Stable plus other EVM networks, or if OFAC screening is a hard requirement.
* Self-host if you need full control over settlement policy, want to keep payment data in your own environment, or expect volume that justifies the operational overhead.
* Both facilitators settle x402 on Stable today. The same `/settle` endpoint can also serve as the on-chain submission target for an MPP server, since MPP's wire format only differs from x402 on the client ↔ resource-server hop. See [Build an MPP endpoint on Stable](/en/how-to/build-mpp-endpoint).

***

Have an agentic payments integration with Stable? Reach out at [bizdev@stable.xyz](mailto:bizdev@stable.xyz).