MCP vs API: What Is the Difference?

What is an API?

An API (Application Programming Interface) lets you write code that talks to a service. You send a request, you get data back. You control what happens.

APIs are for developers. Full control, but you write every line of the integration yourself.

What is MCP?

MCP (Model Context Protocol) lets AI assistants connect to services directly. No developer in between.

Instead of you writing code that calls an API on behalf of your AI, MCP lets the AI call the service itself. It reads your notes, creates new ones, searches your content. All inside a conversation.

The key difference

The fundamental difference is who initiates the call and who handles the logic.

Put simply: APIs are for your code. MCP is for your AI.

When to use each

Use the API when:

• You are building an app that reads or writes data in code
• You want to automate workflows outside of a chat
• You need full control over requests and error handling
• You are bulk-importing or exporting notes

Use MCP when:

• You want Claude or ChatGPT to access your notes directly inside a conversation
• You want your AI to pull in context from past work without you copy-pasting it
• You want to set it up once and forget about it

How Hjarni uses both

Hjarni offers a REST API for developers and a built-in MCP server for AI assistants. They are complementary.

A typical workflow: use the API to bulk-import notes from another tool. Then connect Claude via MCP so it can search and use them in every conversation.

Give your AI a memory