AI integration

REST / OpenAPI vs MCP (Model Context Protocol)

Every enterprise already has REST APIs. Why add MCP?

Quick verdict

REST for machine-to-machine integration and public APIs. MCP for AI-agent access to internal tools with auth, allowlisting and audit baked in.

What each actually does

REST APIs are the default enterprise integration surface. They're not designed for LLM agents — every LLM tool has to write its own connector, handle auth, and hope the OpenAPI spec is accurate.

MCP is a purpose-built protocol for LLM-to-tool communication: standard schema, standard auth pattern, tool discovery, and audit built-in. Any MCP-aware client (Claude Desktop, Cursor, ChatGPT Desktop, custom copilots) can use any MCP server.

REST isn't going away. MCP sits on top or alongside — often wrapping existing REST APIs into an AI-friendly surface.

REST / OpenAPI

The standard machine-to-machine integration surface. Enterprise APIs, third-party SaaS, everything in between.

Strengths
  • Universal
  • Mature tooling and standards
  • Every system has one
  • Well-understood auth patterns
Weaknesses
  • Not AI-native
  • Auth patterns vary widely
  • Tool discovery is manual
  • OpenAPI specs often incomplete

MCP (Model Context Protocol)

Open protocol from Anthropic for LLM-to-tool communication with built-in discovery, auth and audit.

Strengths
  • Purpose-built for LLM agents
  • Standardised tool discovery
  • Client-agnostic (works with Claude, Cursor, custom)
  • Auth and audit patterns built-in
Weaknesses
  • Younger ecosystem
  • Fewer off-the-shelf servers than REST APIs
  • Requires servers to be written / adopted
  • Not for machine-to-machine outside AI context

Side-by-side

CriterionREST / OpenAPIMCP (Model Context Protocol)
PurposeGeneral M2MLLM ↔ tools
Tool discoveryManual per clientStandard, automatic
AuthVaries wildlyStandardised patterns
AuditYou build itServer-side, standard
Ecosystem ageDecadesEmerging (2024–)
Reuse across AI clientsRebuild per clientWrite once, use anywhere

Choose REST / OpenAPI when

  • Standard machine-to-machine integration
  • Public APIs for third-party developers
  • Existing well-adopted API surface
  • No AI in the loop

Choose MCP (Model Context Protocol) when

  • Exposing internal tools to LLM agents
  • Multiple AI clients (Claude, Cursor, internal)
  • Centralised auth, allowlist, audit needed
  • Future-proofing for agentic AI
The pragmatic answer

Use both, on purpose

The winning pattern in 2026: keep REST APIs as-is and wrap the AI-relevant ones in MCP servers. The MCP server enforces per-user auth, tool allowlisting and audit; the REST API stays untouched.

Frequently asked questions

Do I have to migrate my REST APIs?

No. MCP servers typically wrap REST APIs, translating tool calls into REST calls with proper user identity and scoping.

Is MCP secure enough for enterprise?

Yes when servers implement per-user auth, tool allowlisting, rate limits and audit logging — all standard patterns in the reference implementations.

Will REST become obsolete for AI?

No. REST remains the standard for M2M and public APIs. MCP is the AI-specific layer on top of it.

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