MCP vs API: What's the Difference (and Which One You Need)
APIs are for code calling services. MCP is for AI models calling tools. What each is for, when you need which, and why MCP removes the integration work.
What an API does
An API defines endpoints: your application sends a request in a documented shape, the service answers. It is precise and powerful, but every integration is bespoke. Connecting your app to Stripe, then Notion, then a video model means three different auth schemes, three SDKs and three sets of docs. The API itself is not the problem: the wiring is.
What MCP does
MCP standardizes how an AI client (Claude, ChatGPT, Cursor, any agent) talks to tools. Each MCP server exposes named tools with a schema the model already understands: the client asks "what can you do?", reads the tool list, and calls them during a conversation. Add a new server and every tool inside it works immediately, with no per-integration code. The full MCP explainer covers the protocol itself.
Side by side
- Who calls it: APIs are called by your code; MCP servers are called by the AI model inside a client.
- Setup: an API integration is a dev project; an MCP connection is a settings page and an OAuth click.
- Discovery: APIs need docs; MCP clients discover a server's tools automatically.
- Portability: an API integration works in your app only; an MCP server works in every MCP client at once.
When you need an API, when you need MCP
Need an API: you are building your own product or backend that calls a service programmatically, on your own schedule and logic. That does not change.
Need MCP: you want an AI assistant to do things for you, like read your Notion, file a Linear issue or generate an image, without building anything. That is what MCP exists for.
The practical version: if your goal is "ChatGPT, make me a 5-second video" or "Claude, summarize this Drive folder," you do not write against an API at all. You connect an MCP server and ask. Krater's MCP server is that pattern for media work: one connection gives your assistant image, video, voice and document tools backed by 500+ models.
Do they compete?
No. Most MCP servers are a friendly layer on top of existing APIs: the server translates the model's tool calls into API requests behind the scenes. MCP changes who does the wiring, not what runs underneath.
Frequently asked questions
Is MCP replacing APIs?
No: MCP servers usually wrap APIs. APIs keep serving software-to-software work; MCP serves model-to-tool work.
Can I use an API without MCP?
Of course: APIs are not going anywhere. MCP only matters when the caller is an AI model rather than your own code.
Do I need to code to use MCP?
No. Connecting an MCP server is a settings flow in your AI client, not a development task.