x402 vs MPP: Which HTTP 402 Payment Protocol Should Your AI Agent Use? (2026)

Short answer: x402 and MPP are both open specifications that use the HTTP 402 Payment Required status code to let a server charge an AI agent for a resource, and MPP's SDK can also run x402 "exact" payment flows. Pick x402 if you need the protocol with the longer track record and Linux Foundation governance; pick MPP if you're already on Stripe and want stablecoin, card and buy-now-pay-later settlement through one integration.

Last updated 2026-09-29. Both protocols are changing quickly; every claim below is sourced from each project's own documentation, checked on the date noted.

What each protocol is

x402 was contributed by Coinbase and describes itself as "an open‑source protocol that turns the dormant HTTP 402 Payment Required status code into a fully‑featured, onchain payment layer for APIs, websites, and autonomous agents" (x402 FAQ). It launched in May 2025 and, as of its V2 announcement, "has processed over 100M payments across APIs, apps, and AI agents" (x402 V2 launch post). Governance moved from Coinbase to the independent x402 Foundation, which the Linux Foundation "announced the operational launch of" on July 14, 2026, with "40 organizations" as members (Linux Foundation press release).

MPP (Machine Payments Protocol) is "an open standard, internet-native way for agents to pay—co-authored by Tempo and Stripe," announced March 18, 2026. Stripe describes it as providing "a specification for agents and services to coordinate payments programmatically, enabling microtransactions, recurring payments, and more" (Stripe blog). Its own site, mpp.dev, states more simply: "MPP lets agents pay for services on the web, extensible to any payment method" (mpp.dev).

Both projects now interoperate at the SDK level: MPP's own changelog reports that as of June 8, 2026, "MPP now supports generic EVM payments and x402 exact flows from one SDK" (mpp.dev), and Stripe's agentic commerce docs list "MPP or x402" as the two protocols behind its "Accept machine payments" integration path (docs.stripe.com/agentic-commerce).

Side-by-side comparison

x402 MPP
Origin Contributed by Coinbase Developer Platform (x402 FAQ) Co-authored by Tempo and Stripe (Stripe blog)
Announced May 2025 (x402 V2 launch post) March 18, 2026 (Stripe blog)
Governance (2026) x402 Foundation under the Linux Foundation, operational launch July 14, 2026, 40 member organizations (Linux Foundation) Not documented as a separate foundation in the sources reviewed; mpp.dev references its own "Governance" and "IETF Specs" pages, which we did not independently verify for this article
License Apache-2.0 (x402 FAQ) Not documented in the pages reviewed
Settlement — crypto ERC-20 / SPL tokens (e.g. USDC) on Base, Base Sepolia, Solana, Solana Devnet; V2 adds broader "stablecoins & tokens across Base, Solana, other chains, and new L2s" (x402 FAQ; V2 launch post) Stablecoins, via Stripe PaymentIntents with a crypto payment method on the Tempo network (Stripe blog)
Settlement — fiat/cards "Not natively. However, facilitators or third‑party gateways can wrap x402 flows with on‑ and off‑ramps." V2 adds facilitator compatibility with "ACH, SEPA, or card networks" (x402 FAQ; V2 launch post) "Fiat with cards and buy now, pay later payment methods via Shared Payment Tokens (SPTs)," natively through Stripe's PaymentIntents API (Stripe blog)
SDK languages TypeScript, Python and Go as reference implementations, "but x402 is an open protocol" — the buyer quickstart also ships chain-specific packages (Solana, Algorand, Aptos, Stellar, Hedera, TON, NEAR, XRPL and more) (x402 FAQ; Quickstart for Buyers) TypeScript (mppx), Go (MPP-go), Ruby (MPP-rb), Rust (MPP-rs) and Python (PyMPP) (mpp.dev)
Request/response flow Agent "makes a request," "parses the PAYMENT-REQUIRED header," "signs a payload via the x402 client SDKs," then "retries with the PAYMENT-SIGNATURE header" (x402 FAQ) "Servers request payment when you hit a paid endpoint; clients pay; servers verify and return the resource." Stripe's version: the service "responds with a payment request," "the agent authorizes the payment," and "the resource is delivered to the agent" (mpp.dev/quickstart; Stripe blog)
Settlement trust model Every payload "is signed by the buyer and settled directly onchain"; a facilitator that tampers "would fail signature checks and would not be able to settle the transaction" (x402 FAQ) Not documented in the pages reviewed at the same level of detail; Stripe positions itself as the payment processor recording the transaction ("these payments appear in the Stripe API and Dashboard like any other transaction") (Stripe blog)
Spend controls documented Not documented in the FAQ, quickstarts or V2 launch post we reviewed Tempo "access keys" — "delegated signing keys authorized by a wallet on Tempo" — that can set "token spending limits," "limitations for specific contracts or functions," "recipient restrictions" and "future-dated expiration dates" (mpp.dev)
Maturity signal "Over 100M payments" processed by the time of the V2 announcement; V2 spec published December 11, 2025 (V2 launch post) Announced March 18, 2026; mpp.dev's own blog shows active iteration through at least August 12, 2026 (sessions, relays, identity support) (mpp.dev)
Where Stripe supports it Listed as one of the two protocols ("MPP or x402") behind Stripe's "Accept machine payments" integration (docs.stripe.com/agentic-commerce) Same listing — Stripe supports both under the same "Accept machine payments" path (docs.stripe.com/agentic-commerce)

Choose x402 if…

  • You want on-chain stablecoin settlement with the longest operating history of the two: over 100M payments processed and multi-chain support today (Base, Solana, and more) (x402 V2 launch post).
  • You want a protocol under independent, vendor-neutral governance rather than tied to a single payments company. The x402 Foundation sits under the Linux Foundation, with 40 member organizations spanning Coinbase, Stripe, Visa, Mastercard, AWS and others (Linux Foundation press release).
  • Your stack is already crypto-native and you don't need fiat settlement to be native to the protocol — the x402 FAQ is explicit that fiat off-ramps are "not natively" supported and go through third-party gateways (x402 FAQ).
  • You need reference SDKs in multiple non-EVM ecosystems (Solana, Aptos, Stellar, XRPL, TON, NEAR and more are all listed in the buyer quickstart) (Quickstart for Buyers).

Choose MPP if…

  • You're already integrated with Stripe and want agent payments to settle the same way human payments do — Stripe says "these payments appear in the Stripe API and Dashboard like any other transaction," including "tax calculation, fraud protection, reporting, accounting integrations, and refunds" (Stripe blog).
  • You need native fiat, card, and buy-now-pay-later settlement in the same protocol as stablecoins, rather than bolting on a separate off-ramp — MPP settles "in stablecoins as well as fiat with cards and buy now, pay later payment methods via Shared Payment Tokens (SPTs)" (Stripe blog).
  • You want documented, out-of-the-box spend controls at the wallet layer: Tempo access keys can cap spend per token, restrict which contracts or recipients an agent can pay, and expire on a schedule, all without a custom policy engine (mpp.dev).

Use both if…

Stripe's own documentation treats MPP and x402 as parallel options under the same "Accept machine payments" integration path, not as mutually exclusive choices (docs.stripe.com/agentic-commerce). MPP's SDK changelog confirms interoperability at the protocol level: as of June 8, 2026, "MPP now supports generic EVM payments and x402 exact flows from one SDK" (mpp.dev). If you sell to a mix of agents — some paying with x402-native stablecoin wallets, others transacting through Stripe-integrated agent platforms — supporting both from day one avoids picking a rail your buyers don't have.

Controls you still need

Neither protocol's spend-control documentation, on its own, tells you what a specific agent is allowed to do across every tool it calls. x402's own FAQ and quickstarts don't document per-agent caps or allowlists; MPP's Tempo access keys give you per-key spending limits, contract/function restrictions, recipient restrictions and expiration, but you still have to decide which key belongs to which agent, and you still need a record of what was actually paid and why, across whichever protocol a given counterparty uses.

Pink Agentic AI Payment (early access) enforces per-agent spending caps, allowlists and approval thresholds at the MCP layer, before a payment executes.

That means the caps, allowlists and idempotency checks live above the payment rail, so the same rule set can apply whether a given transaction ultimately settles over x402, MPP, or another rail your agents use.

FAQ

Is MPP compatible with x402? Yes, at the SDK level. MPP's own site reports that as of June 8, 2026, "MPP now supports generic EVM payments and x402 exact flows from one SDK" (mpp.dev), and mpp.dev's docs navigation includes a dedicated guide titled "Use MPP with x402" (mpp.dev/quickstart).

Do I need crypto to use MPP? No. Stripe's announcement says businesses can "accept payments directly from agents, in stablecoins as well as fiat with cards and buy now, pay later payment methods via Shared Payment Tokens (SPTs)" (Stripe blog).

Who governs x402? The x402 Foundation, operating under the Linux Foundation. The Linux Foundation "announced the operational launch of the x402 Foundation" on July 14, 2026, with 40 member organizations, including premier members Adyen, AWS, Circle, Cloudflare, Coinbase, Google, Mastercard, Stripe and Visa (Linux Foundation press release).

Does x402 support fiat payments? Not natively, per its own FAQ: "Not natively. However, facilitators or third‑party gateways can wrap x402 flows with on‑ and off‑ramps." x402 V2 adds facilitator compatibility with "legacy payment rails" including "ACH, SEPA, or card networks," but this still runs through facilitators rather than being built into the core payment scheme (x402 FAQ; V2 launch post).

Which protocol has documented spend controls for agents? Of the pages we reviewed, MPP's "Managing agent spend" guide is the one with explicit, documented controls: Tempo access keys can set "token spending limits," "limitations for specific contracts or functions," "recipient restrictions" and "future-dated expiration dates" (mpp.dev). We did not find an equivalent spend-control guide in the x402 FAQ, quickstarts or V2 launch post.

Related

Sources

Disclosure

This guide is published by PinkWallet, which is building Pink Agentic AI Payment (early access): an MCP server that lets AI agents pay, plus a console where companies set spending rules. We are not neutral in this space, which is why every factual claim above links to a primary source.