MCP vs API
What MCP and a normal API each do, how they differ, and which one you need to connect an AI app to your tools.
An API is the way your code talks to one service. MCP is an open standard that lets an AI app such as Claude or ChatGPT connect to external tools and data in the same way.
They are not rivals, because an MCP server often calls a service's API underneath. If you want an assistant to use a tool, you need MCP. If you are building software, you call the API.
Good for
- People new to AI tools who keep hearing both terms
- Developers deciding whether to build an MCP server or call an API directly
- Teams choosing how to connect Claude or ChatGPT to internal systems
Side by side
Use an API when you are writing code that calls a service, and MCP when you want Claude, ChatGPT or an editor to use a tool without code. Claude's own API can also call remote MCP servers.
| Option | A regular API | MCP |
|---|---|---|
| Who it is for | Code that calls one service | AI apps (clients) that connect to many tools |
| What defines it | Each service sets its own endpoints and data shapes (Claude API: one endpoint list) | One shared protocol for every server: tools, resources, prompts |
| Message format | Set by the service (Claude API: JSON over HTTPS, RESTful) | JSON-RPC 2.0 |
| Transport | Set by the service (Claude API: HTTPS) | stdio (local) or Streamable HTTP (remote) |
| Finding what is available | Read the service's docs (Claude API: API reference) | Client asks the server: tools/list, server/discover |
| Credentials | Set by the service (Claude API: an API key or federated token) | Streamable HTTP supports standard HTTP auth such as bearer tokens |
| Works across AI apps | Not defined by the API itself | Yes: Claude, ChatGPT, VS Code, Cursor and others support MCP |
| Reaches an API underneath | Is the API | A server can wrap an API or a database |
Which to pick
Our advice: use MCP to let an AI app use a tool, and use the API to write software that calls a service. The MCP site describes one protocol that clients like Claude and ChatGPT share, while each regular API is defined by its own service.
MCP does not replace APIs. Most MCP servers still call an API to do the work.
Best for
- MCP: people who want Claude or ChatGPT to use their apps without writing code
- MCP: teams that want one connection to work in several AI apps
- API: developers building their own product on a model or service
- API: batch jobs and backend code with no AI app in the loop
Skip it if
- MCP: you are writing plain backend code that never talks to an AI app
- API: you want a non-developer to connect a tool inside chat
Questions
What is the difference between MCP and an API?
An API is a service's own interface that your code calls. MCP is an open standard for connecting AI applications to external systems, so one connection style works across AI apps. An MCP server often calls a normal API underneath.
Does MCP replace APIs?
No. MCP sits in front of tools and data so AI apps can use them. The service behind an MCP server usually still exposes an API.
When should I use MCP instead of an API?
Use MCP when an assistant, such as Claude or ChatGPT, should use a tool for you. Use an API when your own code needs to call a service directly.
Is MCP an API?
Not in the usual sense. MCP is a protocol that defines how an AI app (the client) and a tool (the server) exchange messages. Its data layer is based on JSON-RPC 2.0, and servers run over stdio (local) or Streamable HTTP (remote).
Can Claude's API use MCP servers?
Yes. The Claude Messages API has an MCP connector in beta that connects to remote MCP servers without a separate MCP client. Anthropic says only tool calls are supported, and the server must be exposed over HTTP, so local stdio servers cannot be connected directly.
Do I need to know how to code to use MCP?
No. In apps like Claude you add an existing server by name or URL. You only write code if you build a new server. See what MCP is and what an MCP connector is.
What is an MCP server?
A program that provides context and tools to AI apps. It can run on your computer (local) or on the vendor's side (remote). Browse the servers on PlugWiki to see examples.
Which AI apps support MCP?
The MCP site lists AI assistants like Claude and ChatGPT and development tools like Visual Studio Code and Cursor. Setup steps are in Claude Code MCP setup and ChatGPT MCP setup.
Sources
Docs, issue trackers and discussions this page is built from.
Show all 4Hide
- What is MCP? · modelcontextprotocol.io
- Claude API overview · platform.claude.com
- MCP architecture overview · modelcontextprotocol.io
- MCP connector · platform.claude.com