MPP's supposed to eventually work with more than Stripe.
david_shi•Mar 18, 2026
It seems like this is designed for atomic purchases, could it be extended for subscriptions?
jacobn•Mar 18, 2026
> MPP provides a specification for agents and services to coordinate payments programmatically, enabling microtransactions, *recurring payments*, and more.
I believe the Shared Payment Token is interchangeable with a payment method id that you attach to a customer object, but that link has very sparse information about how things actually work end to end and what objects mean what.
lihorne•Mar 18, 2026
Hey, I'm one of the developers at Tempo. We're working on an extension type for subscriptions to propose being added to the spec as well! We're starting with the simple types, but subscriptions are a natural extension. The subscription intent will work similarly to a one-time charge—the server returns a 402 with intent="subscription", and the client signs a recurring authorization.
david_shi•Mar 18, 2026
Cool, would be nice to get specifics on how payments are processed, failures, and cancellations re: the recurring model.
codeulike•Mar 18, 2026
You're absolutely right! I should have sent $5.00 for that transaction and not $500,000. I will generate a letter for you to print and sign and send to your bank to notify them of my mistake. Would you like me to generate a bankruptcy filing for you as well?
ezekg•Mar 18, 2026
LLMs rarely admit fault, you gotta shift blame onto the user:
> You're absolutely right! The transaction was submitted as $500,000 instead of $5.00. Since that's what was entered on your end, you'll need to contact your bank to resolve it. I will generate a letter for you to print, sign, and send to your bank if needed. Would you like me to generate a bankruptcy filing for you as well?
leptons•Mar 18, 2026
Claude always says it is sorry for screwing up when I point out that it screwed up.
fragmede•Mar 18, 2026
"Never apologize" into the customized instructions seems to work well for that specific issue.
leptons•Mar 18, 2026
This is the funniest (but seriously not funny at all) thing I've seen on the internet since the start of the whole "AI" craze. And it's all too true.
What does this actually have to do with agents? What does the protocol include that makes this useful with AI rather than just a boring old program?
uxhacker•Mar 18, 2026
And would it not be useful to have some kind of human in the middle? For example what is to stop charge backs if no human has actually authorized the transaction?
XzAeRosho•Mar 18, 2026
There's a slightly new topic called Agentic Commerce, where you say for example: "purchase for me the most energy efficient dishwasher with a budget of $600", and the agent will connect via specialized via special MCP Servers and APIs to available stores, and will do the full purchase process for you.
This MPP helps bridge the gap between the agent putting the product "in the basket", to actually completing the full purchase process.
Disclaimer: I'm not in any way advocating for this use case, but it's part of my job to understand how it works. Part of what I do is try to help Agents understand, for example, what is "an efficient dishwasher" using actual data, and not hallucinated info.
seanmcau•Mar 18, 2026
I'm probably overlooking something, but what makes the problem of being able to get from item in basket to item is shipping different from choosing which item(s) to put in the basket?
In other words, if Agents are able to navigate marketplaces, shouldn't that imply they can also navigate a subset of the marketplace, the payment section? Especially given that that section is "easier: theres no need for qualitative (or quantitative) judgement like there is for the shopping portion.
Perhaps its a matter of proper safeguards?
XzAeRosho•Mar 18, 2026
It's not actually doing browser actions like Playwright or other browser automation tools, rather than direct API and MCP calls/actions. This is a whole new subset of API and connections that are all contained within the Agent context, no browser mocking. That's why they are creating these new protocols, so the full governance can work within the context of the Agent and its available tools.
As I said, it doesn't have to make sense, but this is being pushed on us anyway...
pythonaut_16•Mar 18, 2026
Thanks for sharing your insights!
It seems like this workflow suffers the same problem as Alexa and Amazon dash buttons: consumers don't typically want the computer to just go buy things for them with no oversight. At least I don't.
Adding a checkout step would make this more plausible to me. "Agent, go find the most efficient dishwasher under $600" where it adds its recommendation to a cart, or even "Find me the best dishwashers under $600" where it creates a catalog page with its recommendations and an easy checkout process with whatever store is actually providing.
twalla•Mar 18, 2026
As much as I detest having to look at ads or being "influenced" in any way, shape or form, I think the opportunities for exploitation with what you just described is potentially orders of magnitude more harmful. Sure, let me just hand my wallet to a stochastic black box with god-knows-what RL'd biases and then hook it up to adversarial data sources all vying to extract the most money from me - what could possibly go wrong?
whalesalad•Mar 18, 2026
This still does not answer the question. What makes this different from any other API request to Stripe?
ezfe•Mar 18, 2026
That's why it's called Machine Payments Protocol, instead of Agent Payments Protocol
naomi_kynes•Mar 18, 2026
MPP handles 'how do agents pay', but not 'did anyone authorize this'. For low-value API calls that's fine. But once agents start chaining transactions, you need a channel where the agent can ask a human 'I'm about to spend $2k on this, still in scope?' before the payment happens - not a fraud alert after. The authorization layer is a separate infrastructure problem from the payment protocol.
rvz•Mar 18, 2026
This is a good standard that I can get behind [0] since it's a serious proposal and submitted to the IETF [1] for MPP for machine-to-machine payments.
A well thought out proposal for the long term, unlike MCP which is a complete joke of a "standard" and broken by design.
Curious since I haven't followed super closely: what's busted about MCP?
btown•Mar 18, 2026
Jokes about wallet-draining aside, we're already giving our agents a real cash budget that they use for tokens. Our harnesses have mechanisms to manage that spend. And having an easily detectable protocol would allow the harness to ensure that its deterministic code is in play to make these payments - you'd give your payment details to the harness, not to the agent itself.
And as to use cases, if I want quality outputs for automated research and discovery of a topic, in a world where quality journalism/scholarship should be compensated and does use tools like Cloudflare to block automated access, and where AI-generated content is everywhere, it's optimal for me to want to spend some amount of the money I spend on tokens, on the ability for my agent to access reputable primary and secondary sources as needed.
The challenge, of course, is that now there's an incentive for a spam source to try to get my agent to pay it, rather than the actual creator of the content. But there are interesting ways to solve this, because with these payment rails there's now an incentive for alliances of content creators to maintain indices of reputable sources and their canonical domains - perhaps even authoritative hashes of content. Lots of possibilities here.
zer00eyz•Mar 18, 2026
> we're already giving our agents a real cash budget that they use for tokens.
I read this line and my (poor little) brain ran in a whole other direction for a moment. Because AI token management and "parental controls" aren't that far separated functionally.
How far are we from the AI companies selling token packs like video games sell premium currency? Buy NOW, 1.99 for 10,000 Anthropic gold...
ccozan•Mar 18, 2026
Last thing I heard: stock options are so last year, AI companies award ... tokens now. Can't find the source now, sorry!
btown•Mar 18, 2026
There was another comment I recall from today, discussing how OpenAI is not-so-subtly adopting a social-network-esque model, in how it's fine-tuned its chat system to always suggest another question that the user might want to ask.
And the gacha gaming industry knows exactly how to monetize this kind of trained instinct in a userbase. One might even call it a sense of pride and accomplishment...
(But, to my larger point, if agentic harnesses can offer their LLMs a source of reputable input tokens from professional content providers, as an alternative to just more token back-and-forth with the model provider... that harness can at least direct some of that money towards producers of well-researched content.)
vicchenai•Mar 18, 2026
the real question for me is what happens when agents start hitting premium data APIs with MPP. right now if i want my agent to pull realtime financial data it has to go through my API keys with monthly billing. with MPP the agent could theoretically pay per-query directly to data vendors. thats a much better model for bursty workloads but the authorization problem naomi_kynes raised is real - you need spending caps that the agent cant override, not just logging.
xmly•Mar 18, 2026
Fascinating — this is the future of decentralized finance. Agents will be the entities that both earn and consume.
film42•Mar 18, 2026
Maybe. When it comes to actual payments, fee structures don't allow for this outside of the laboratory.
4k0hz•Mar 18, 2026
"Decentralized" seems like a stretch for something developed and promoted by monolithic payment processors.
gavinray•Mar 18, 2026
I fail to see how "API call" is anything inherent to Agents/LLMs?
Is this an attempt to get multiple payment processors to adopt the same Payments API so that agents fail less often?
ezfe•Mar 18, 2026
It has nothing to do with Agents/LLMs which is why it's not called "Agentic Payment Protocol."
It's an API for making purchases instead of interacting with a website of unknown flow.
gavinray•Mar 18, 2026
The text literally starts with:
> We believe agents will become an integral part of the internet economy, and they need the ability to transact with businesses and one another.
> MPP provides a specification for agents and services to coordinate payments programmatically, enabling microtransactions, recurring payments, and more.
ezfe•Mar 18, 2026
Obviously agents are the big thing right now, but that doesn't change the fact that MPP is an automation solution
neya•Mar 18, 2026
I feel like the word "protocol", is just abused like it is a glorified marketing term. Kind of like how the word "hacker" was abused in everything else that had nothing to do with hacking.
MCP was just a glorified way of tool calling but generated so much hype (and it eventually died down). Now we have MPP. Which again - could have just been another tool call exposed to the agent.
Imagine you hire someone who claimed to have invented a new protocol and you're thinking of something like TCP or UDP, but all they share is just a markdown file.
I almost was going to point it out as evidence there was thought put into it. Nope, it's flimsy and AI generated.
Also, it contains provisions for scamming customers:
> 403 indicates the payment succeeded but access is denied by policy
No, it doesn't explain how to refund payments for customers you deny access to.
Xirdus•Mar 18, 2026
This one is even worse IMO
> Servers MAY return 402 when:
> * Offering optional paid features or premium content
This implies that a successful GET request to a resource that user already does have access to, might still return 402 instead of 200. This makes 402 basically unworkable.
pertsix•Mar 18, 2026
An RFC is a request for comments, contributions.
Are you open to contributing to this RFC?
pear01•Mar 18, 2026
Was it AI generated? If so, should I just delegate my AI to do so?
john_strinlai•Mar 18, 2026
that doesnt sound nearly as fun as getting upvotes, if im honest
darkwater•Mar 18, 2026
Will they get a slice of the earnings in return by Stripe?
brendan_j_ryan•Mar 18, 2026
Hey! [0]
Am the primary author of the core spec, alongside many others at Tempo and Stripe [0].
As is customary with the IETF draft process, this is our first submission and we expect that we will continue to iterate with the broader community -- including yourself if you are interested in contributing [1]
Thanks for feedback on those two points.
Re: Refunds: This is a payment method specific implementation detail. e.g. this looks very different on cards vs. bank accounts vs. stablecoins. We will provide stronger guidance here to remove ambiguity in the spec
Re: 403: This provision comes from the ability to have _multiple_ Authentication headers, which we view as a necessity for real-world utilization and also compatibility with the Authentication scheme. Similar to the above, we will provide stronger guidance for servers which may support a plurality of authentication schemes and need to handle this edge case.
[0] Had to create a new account since it turns out many years ago I never set an email on my HN profile...
Be honest... Have you used AI to generate this "spec"?
NetOpWibby•Mar 18, 2026
I recently redesigned my blog to look like a modern RFC and I'm loving the way they've decided to render tables in their plain text, definitely gonna steal that.
On topic though, Stripe is trying to make themselves the Visa/Mastercard of crypto. They're in position to do so and it seems like Coinbase is their other half. I don't trust or like it though.
Oh wow, I never heard of this. I'm currently working on something similar with the same 1% rate, haha! WELP
treyd•Mar 18, 2026
I think this started when "web3" cryptocurrency projects started using the term to pretend that something which isn't much more than a service that uses a blockchain network to move money around was actually somehow "decentralized" and that that made it more trustworthy.
devmor•Mar 18, 2026
I've been thinking this, but never really put it into words.
Every time I see one of these I think "You are just describing an API".
notatoad•Mar 18, 2026
"protocol" is just an agreement to communicate in a standardized way. this is a protocol. a tool call exposed to the agent is a protocol - the act of "exposing it to the agent" means you're defining a protocol.
there's nothing wrong with calling this a protocol. the problem is in hyping it up as though every protocol is going to be world-changing on the level of TCP.
sutib•Mar 18, 2026
"they need the ability to transact with businesses and one another."
Really, they _need_ it. How can we possibly live without computers spending money without supervision?
user3939382•Mar 18, 2026
The more industrial activity and investment I see in “payments” and ecommerce, is to me a signal of a hollow society that has ceased creating real value. We have more to contribute than materialism, skimming off of electronic transactions, entertainment etc.
quantium1628•Mar 18, 2026
the comments here are better than the article lol
Animats•Mar 18, 2026
"Creates a direct connection between your wallet and our bank account!"
Note the absence of invoices, bills of lading, and receipts,
all the things you need when a vendor doesn't deliver.
All it does is send money, one-way. So it's useless in a B2B context.
fhn•Mar 18, 2026
All payments are final. Cancellations and refunds will be charged a 5% processing fee.
glitchc•Mar 18, 2026
It feels like an attempt to bypass PCI-DSS...
giovannibonetti•Mar 18, 2026
For those of you in Brazil, my company jota.ai has built a financial AI-assistant that you can chat with to open a bank account, connect with accounts from other banks, make instant Pix payments with any of them, all of that through WhatsApp right now. We're working hard to release long-running agents soon that can do increasingly complex workflows involving payments and whatnot.
Please let us know if you have suggestions of what complex workflows you would like to build.
ImPostingOnHN•Mar 18, 2026
How do you keep customer information, credentials, and access secure from your employees (including yourself)?
rickydroll•Mar 18, 2026
As soon as you have a fungible currency, I expect that, from past experience, everyone who carries those packets will stick out a hand for a piece of the action. From a brief read of the description, I also expect attackers to work out a way to drain your account without you noticing.
Regulation E limits your losses for electronic banking. Is this new payment system covered by Regulation E? What is the maximum loss a consumer would experience?
Christhepurr86•Mar 18, 2026
old article but still relevant. some things don't change
grigio•Mar 18, 2026
There are more competing "payment protocols" than users
davidliu847386•Mar 18, 2026
tldr for anyone skimming: the key insight is in section 3
vishnuharidas•Mar 18, 2026
Okay, I am NEVER letting an agent make payment autonomously. If there's a payment that has to be made, tell me, I will do that myself.
benced•Mar 18, 2026
This isn't incompatible with the agent placing the purchase. I already let Claude Code do _most_ of what it wants but make it ask permission before sending a message on Slack. An LLM having the capability to do X is not incompatible with it being deterministically forced to seek permission to do X.
Seventeen18•Mar 18, 2026
Not everything must be a protocol. I believe we will see very interesting attacks vectors in the incoming years, especially when we see how unsafe are most of the agents harness.
crowcroft•Mar 18, 2026
Where does this fit in alongside the Agenctic Commerce Protocol? Is it just a question of whether your transacting bits vs atoms?
26 Comments
Yeah I read that copy too, did you read the spec?
> You're absolutely right! The transaction was submitted as $500,000 instead of $5.00. Since that's what was entered on your end, you'll need to contact your bank to resolve it. I will generate a letter for you to print, sign, and send to your bank if needed. Would you like me to generate a bankruptcy filing for you as well?
This MPP helps bridge the gap between the agent putting the product "in the basket", to actually completing the full purchase process.
Disclaimer: I'm not in any way advocating for this use case, but it's part of my job to understand how it works. Part of what I do is try to help Agents understand, for example, what is "an efficient dishwasher" using actual data, and not hallucinated info.
In other words, if Agents are able to navigate marketplaces, shouldn't that imply they can also navigate a subset of the marketplace, the payment section? Especially given that that section is "easier: theres no need for qualitative (or quantitative) judgement like there is for the shopping portion.
Perhaps its a matter of proper safeguards?
As I said, it doesn't have to make sense, but this is being pushed on us anyway...
It seems like this workflow suffers the same problem as Alexa and Amazon dash buttons: consumers don't typically want the computer to just go buy things for them with no oversight. At least I don't.
Adding a checkout step would make this more plausible to me. "Agent, go find the most efficient dishwasher under $600" where it adds its recommendation to a cart, or even "Find me the best dishwashers under $600" where it creates a catalog page with its recommendations and an easy checkout process with whatever store is actually providing.
A well thought out proposal for the long term, unlike MCP which is a complete joke of a "standard" and broken by design.
[0] https://paymentauth.org/
[1] https://datatracker.ietf.org/doc/draft-ryan-httpauth-payment...
And as to use cases, if I want quality outputs for automated research and discovery of a topic, in a world where quality journalism/scholarship should be compensated and does use tools like Cloudflare to block automated access, and where AI-generated content is everywhere, it's optimal for me to want to spend some amount of the money I spend on tokens, on the ability for my agent to access reputable primary and secondary sources as needed.
The challenge, of course, is that now there's an incentive for a spam source to try to get my agent to pay it, rather than the actual creator of the content. But there are interesting ways to solve this, because with these payment rails there's now an incentive for alliances of content creators to maintain indices of reputable sources and their canonical domains - perhaps even authoritative hashes of content. Lots of possibilities here.
I read this line and my (poor little) brain ran in a whole other direction for a moment. Because AI token management and "parental controls" aren't that far separated functionally.
How far are we from the AI companies selling token packs like video games sell premium currency? Buy NOW, 1.99 for 10,000 Anthropic gold...
And the gacha gaming industry knows exactly how to monetize this kind of trained instinct in a userbase. One might even call it a sense of pride and accomplishment...
(But, to my larger point, if agentic harnesses can offer their LLMs a source of reputable input tokens from professional content providers, as an alternative to just more token back-and-forth with the model provider... that harness can at least direct some of that money towards producers of well-researched content.)
Is this an attempt to get multiple payment processors to adopt the same Payments API so that agents fail less often?
It's an API for making purchases instead of interacting with a website of unknown flow.
MCP was just a glorified way of tool calling but generated so much hype (and it eventually died down). Now we have MPP. Which again - could have just been another tool call exposed to the agent.
Imagine you hire someone who claimed to have invented a new protocol and you're thinking of something like TCP or UDP, but all they share is just a markdown file.
I almost was going to point it out as evidence there was thought put into it. Nope, it's flimsy and AI generated.
Also, it contains provisions for scamming customers:
> 403 indicates the payment succeeded but access is denied by policy
No, it doesn't explain how to refund payments for customers you deny access to.
> Servers MAY return 402 when:
> * Offering optional paid features or premium content
This implies that a successful GET request to a resource that user already does have access to, might still return 402 instead of 200. This makes 402 basically unworkable.
Are you open to contributing to this RFC?
Am the primary author of the core spec, alongside many others at Tempo and Stripe [0].
As is customary with the IETF draft process, this is our first submission and we expect that we will continue to iterate with the broader community -- including yourself if you are interested in contributing [1]
Thanks for feedback on those two points.
Re: Refunds: This is a payment method specific implementation detail. e.g. this looks very different on cards vs. bank accounts vs. stablecoins. We will provide stronger guidance here to remove ambiguity in the spec
Re: 403: This provision comes from the ability to have _multiple_ Authentication headers, which we view as a necessity for real-world utilization and also compatibility with the Authentication scheme. Similar to the above, we will provide stronger guidance for servers which may support a plurality of authentication schemes and need to handle this edge case.
[0] Had to create a new account since it turns out many years ago I never set an email on my HN profile...
[1] https://github.com/tempoxyz/mpp-specs
On topic though, Stripe is trying to make themselves the Visa/Mastercard of crypto. They're in position to do so and it seems like Coinbase is their other half. I don't trust or like it though.
Every time I see one of these I think "You are just describing an API".
there's nothing wrong with calling this a protocol. the problem is in hyping it up as though every protocol is going to be world-changing on the level of TCP.
Really, they _need_ it. How can we possibly live without computers spending money without supervision?
Note the absence of invoices, bills of lading, and receipts, all the things you need when a vendor doesn't deliver. All it does is send money, one-way. So it's useless in a B2B context.
Please let us know if you have suggestions of what complex workflows you would like to build.
Regulation E limits your losses for electronic banking. Is this new payment system covered by Regulation E? What is the maximum loss a consumer would experience?
https://www.agenticcommerce.dev/