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🧭 MCP vs REST Decision Helper

Answer six questions about who uses your interface and how, and get a reasoned recommendation: a REST API, an MCP server, or the most common answer, MCP in front of REST.

1 Who will call this interface?
2 Should callers discover what they can do at runtime: tools, descriptions and parameters?
3 Do you already have a REST (or GraphQL) API for this capability?
4 Do you need HTTP caching, CDNs, webhooks, or public or partner API conventions?
5 Will callers combine several actions in a conversation, with context such as files, documents or prompts?
6 How strict are your governance needs (audit trails, per-user permissions, data residency)?
Your answers stay in your browser (and in the page link, so you can share the result).

Runs in your browser: what you enter is never sent anywhere. We only count anonymous usage, such as which buttons are used, to improve the tools.

How the recommendation works

Each answer adds weight to one of three outcomes. Applications that need stable contracts, caching and partner conventions point to REST. AI agents that need to discover actions and combine them with context point to MCP. When agents need capabilities you already expose to applications, the answer is almost always a thin MCP server in front of your REST API, so business logic and permissions live in one place.

Governance doesn’t change the choice, but it changes how you build it: strict requirements mean the MCP layer must carry each user’s identity through to the API and log every tool call.

Frequently asked questions

What is the difference between MCP and a REST API?

A REST API is a fixed contract that applications call over HTTP. The Model Context Protocol (MCP) is an open standard that lets AI assistants and agents discover and use tools, resources and prompts at runtime. REST serves applications; MCP serves AI agents.

Should MCP replace my REST API?

Usually not. The common pattern is a thin MCP server in front of an existing REST API: the API keeps business logic, authorisation and caching, while the MCP server describes a curated set of actions for agents.

Is MCP secure enough for enterprise data?

It can be, if the MCP server passes the user’s identity through to your existing API and enforces the same permissions, logs every tool call, and only exposes the actions agents genuinely need.

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