A few people asked me recently "Is MCP going to replace REST?" and I kept giving the same answer in the comments. So instead of repeating myself, I decided to write it all down properly, once and for all. These are my thoughts. I'd genuinely love to hear yours too agree, disagree, or somewhere in between. Drop your perspective in the comments as you read along.
Introduction Why This Question Keeps Coming Up
Over the past year, the AI ecosystem has moved fast. MCP (Model Context Protocol), launched by Anthropic on November 25, 2024, gave AI agents a standardized way to connect to tools and data sources. Within months, OpenAI, Google DeepMind, and Microsoft all adopted it making it the de facto standard for AI-to-tool connectivity. Almost immediately, the hot take started circulating "MCP is the next REST. REST is dead."
I understand why people say it. MCP is elegant, developer friendly, and growing fast. It solves a real pain point: before MCP, connecting M AI models to N tools meant M×N custom integrations a combinatorial explosion. Every agent needed its own connector for every tool. It felt like the early REST days a protocol that just made sense.
In December 2025, Anthropic donated MCP to the Agentic AI Foundation under the Linux Foundation cementing it as vendor neutral, open infrastructure. It's no longer just Anthropic's protocol. It belongs to the industry.
But here is the difference between a protocol that simplifies AI tool integration and a protocol that replaces the backbone of enterprise systems. Confusing these two things leads to bad architectural decisions.
In this post, I'll walk through the reasoning step by step who each protocol is actually built for, what history tells us about protocol wars, where Google's brand new UCP fits into all of this, and what the enterprise stack realistically looks like in 2026 and beyond.
Let's break it down.
Before debating whether MCP replaces REST, ask a simpler question: what communication problem does each protocol actually solve?
These are different communication planes.
**Even if enterprises build 1,000 AI agents, their **billing systems, payment gateways, HR platforms, core banking systems, ERP, and CRM will still expose REST or gRPC APIs. MCP doesn't replace that layer and it doesn't want to.
What Actually Happens in an Enterprise
Let's make this concrete. Imagine a tax platform building an AI agent. The architecture doesn't replace REST it wraps around it.
REST still owns: Service contracts · Auth (OAuth2, JWT) · Gateway routing · Observability · Versioning · SLAs
MCP becomes a translation layer, not the foundation protocol.
MCP sits in the middle as a coordination layer it helps the agent decide which tool to call and how to pass context between steps. But below it, REST is still doing what it has always done enforcing service contracts, handling authentication via OAuth2 and JWT, managing gateway routing, providing observability, version control, and SLA guarantees.
Why REST Won't Disappear
REST has accumulated over two decades of enterprise trust. That is not sentiment it is infrastructure. It is transport layer agnostic, HTTP based, language neutral, and supported by a full enterprise toolchain API gateways, WAFs, APIM platforms, rate limiters, and monitoring tools that entire teams are built around.
MCP, by contrast, is AI-specific and model facing. It is purpose built for tool invocation in an agentic context. It has no native auth standard, no SLA model, no enterprise gateway story yet. Its ecosystem is forming rapidly but it is nowhere near the maturity level that regulated industries require.
Different maturity levels do not mean one is better. They mean they belong at different layers of the stack. Betting your banking core on a protocol that is still finding its footing is the wrong call and any senior architect knows it.
The Real Shift That Might Happen
Here is what will change the entry point, not the backbone.
Old world:
UI → REST API → Backend
New world:
UI → AI Agent → MCP → Tools → REST API → Backend
REST becomes invisible to the user but not obsolete. The front door changes; the load bearing walls stay exactly where they are.
This is a familiar pattern. When mobile apps took over, REST adapted. When microservices exploded, REST specialized. When AI agents mature, REST will again shift its role from front door to backbone. It quietly powers the deterministic layer underneath everything new being built on top.
What History Actually Teaches Us
Let's be honest protocols can die. SOAP is the clearest example. Nobody is starting a new SOAP integration in 2026. REST won that fight, and SOAP lost. It earned its retirement.
But here is the nuance worth understanding: SOAP lost because REST solved the exact same problem more elegantly lightweight, stateless, human-readable HTTP versus verbose XML envelopes. They were direct competitors on the same turf. REST won because it was simply better at the same job.
SOAP also did not disappear overnight. It is still buried inside legacy banking, insurance, and government systems built in the 2000s not because it is good, but because replacing it costs millions and carries enormous risk. The lesson there is not that SOAP survived it is that technical debt is incredibly sticky.
Now look at gRPC and GraphQL. Neither killed REST because neither competed on the same ground. gRPC found its lane in high performance internal service communication. GraphQL found its lane in flexible client driven data queries. REST kept everything else. All three coexist comfortably today.
MCP follows the same pattern. It is not competing with REST. It is solving a problem REST was never designed for. A protocol gets replaced only when a better one solves the exact same problem more elegantly. MCP and REST do not solve the same problem and they never will.
When Could MCP Replace REST?
Only under conditions that regulated, deterministic industries will never accept if systems stopped being deterministic APIs, if everything became LLM mediated, if structured contracts disappeared, and if enterprises were willing to accept probabilistic orchestration as their foundation.
Banking, Healthcare, Tax, Insurance, and Government will never accept that. These industries run on strict, auditable, deterministic contracts. Every transaction needs a paper trail. Every API call needs a guaranteed response shape. You cannot run a payment gateway on probabilistic orchestration the regulators alone would shut it down.
For AI native SaaS companies building greenfield products? MCP could absolutely become the primary interface layer. But even there, the underlying data stores, payment processors, and third party integrations will still talk REST.
REST never leaves the stack. It moves from front door to backbone. In 2030, we'll likely be discussing whatever comes after MCP while REST quietly hums away underneath.
Enter Google UCP The Stack Just Got Another Floor
Just when you thought the picture was settled, Google launched UCP (Universal Commerce Protocol) on January 11, 2026 at NRF's Retail Big Show and it proves the layered thesis perfectly.
UCP is an open-source standard for agentic commerce covering the full shopping journey from discovery and cart through to checkout, payments, and post-purchase support. It was co-developed with Shopify, Etsy, Wayfair, Target, and Walmart, and endorsed by over 20 partners including Adyen, American Express, Best Buy, Flipkart, Macy's, Mastercard, Stripe, The Home Depot, Visa, and Zalando.
The problem UCP solves: before UCP, every AI platform needed its own custom integration with every retailer the M×N explosion all over again. UCP gives every AI agent a single integration point to interact with any merchant using a common language.
Here is the critical architectural detail UCP does not fight REST. It explicitly runs on top of it. UCP supports REST as its primary transport binding, alongside MCP for session context, A2A (Agent2Agent) for agent-to-agent delegation, and AP2 for secure payment execution. The updated retail AI stack looks like this:
Notice what happened. REST did not disappear. It moved down one more floor. Each new protocol added a specialized layer above it UCP for commerce orchestration, MCP for tool invocation, A2A for agent delegation, AP2 for payments. Every protocol has its lane. None of them erase the others.
Google's bet with UCP mirrors how HTTP became the web's foundation an open standard, not owned by one company, usable by everyone. Microsoft and OpenAI are building proprietary equivalents. Google went open. That is a meaningful architectural and strategic difference worth watching.
And underneath all of it? REST APIs, quietly doing their job.
The Bottom Line
Instead of saying "MCP is the next REST", the more accurate architectural statement is:
MCP handles AI tool interoperability. UCP handles agentic commerce. REST remains the deterministic backbone underneath both. That is not a replacement that is a maturing, layered stack.
My Honest Take
If enterprises go heavy into AI agents, MCP adoption will grow, agent orchestration will become a critical architectural layer, tool registries will get standardized, and U*CP will reshape how commerce is transacted*. All of that is real and coming fast.
But REST or gRPC remains the deterministic contract layer underneath all of it. MCP is agent native. REST is system native. They operate at different altitudes in the stack, and confusing them is like saying Kubernetes replaced TCP/IP. The analogy collapses on contact with reality.
The right question is never "which protocol wins?" It is always: how do these protocols collaborate to serve different layers of a maturing, AInative enterprise?
That is the conversation worth having.
That's my take. I'd love to hear yours whether you agree, disagree, or see it completely differently from where you sit. Drop your thoughts in the comments. Every perspective makes this richer, and I genuinely read every single one. Let's talk. 💬
Thanks
Sreeni Ramadorai
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