MCP vs API: what's the difference?
MCP vs API: an API is a door into software that a programmer opens by writing code. An MCP lets an AI assistant open it when you ask in plain English.
Short answer
| API | MCP | |
|---|---|---|
| Who uses it | A program a developer wrote | An AI assistant (Claude, ChatGPT, Cursor) |
| How you ask | Exact code: the right address, fields and format | Plain English: "Who owns 412 Elm St?" |
| Who decides the steps | The developer, ahead of time | The AI, at the moment you ask |
| Setup | Write and maintain code | Add a connector, sign in |
| Best for | Fixed, high-volume jobs that run the same way every time | Questions and tasks that change every day |
| Standard? | Every API is different | One protocol for all MCP servers |
How an API call works
An API (application programming interface) is a set of addresses a program calls to get data or act. Each API has its own rules for addresses, fields, sign-in and responses.
A developer reads the docs and writes code that:
- signs in with a key,
- sends a request in the exact format,
- reads the response, and
- handles errors.
How an MCP call works
MCP (Model Context Protocol) is an open standard for connecting AI assistants to software. An MCP server tells the AI what each tool does and needs.
Side by side: the same property lookup
Goal: the owner, last sale and estimated value of 412 Elm Street.
With an API (ATTOM's property API, for example):
With an MCP:
Who owns 412 Elm St, Memphis TN? When did they buy, and what's it worth now?
When you still want an API
Use an API directly when:
- The job is the same every time and runs at volume. Pulling 50,000 records into a spreadsheet nightly is a job for code.
- You need exact, repeatable results. An AI picks its steps each time.
- You're building your own product. If your app shows property data to users, call the API from your app.
- The tool has no MCP server yet. Many real estate tools only have an API, or neither.
Use an MCP when:
- The question changes daily. "Which pre-foreclosures in my county have equity?" today, "who hasn't called back?" tomorrow.
- The task crosses several steps or tools. Find the properties, get the owners, build the list.
- The person asking isn't a developer. An investor or agent can use it on day one.
Many teams use both: an API for the nightly import, an MCP for the daily questions.
Cost and maintenance
APIs usually charge per call or monthly, but the real cost is the code. Someone writes it, fixes it when the API changes and extends it when the job changes.
Is MCP safe to use with my data?
It depends on the server, and a good one uses OAuth instead of a pasted key. It lets you limit what it does and uses only your permissions.
More in MCP security.
Related: ATTOM API and MCP
Questions
Is MCP replacing APIs? No, MCP sits on top of APIs.
Is MCP slower than calling an API directly? Usually a little, since the AI picks a tool and the server adds a step.
Do I need to know how to code to use an MCP? No, in Claude or ChatGPT you add a connector and sign in.
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