Founders meet the words API and MCP every week: the API in a tool's docs and the MCP server in a launch post. ZeroCrew's directory marks which tools offer an MCP server, so the difference matters when you pick what your company runs on. The short version: an API is for code a person writes, and MCP is for an AI agent that works out the steps itself.
MCP and APIs are partners, not rivals. The MCP specification describes tools that let an AI model query databases and call APIs, so an MCP server often sits on top of the API a tool already has. This ZeroCrew guide explains what each one is, where they differ, and which one a founder with zero employees reaches for first.
What is an API?
An API, or application programming interface, is a fixed set of requests one program can send to another. NIST defines an API as a system access point with "a well-defined syntax" that application programs call for "well-defined functionality." On ZeroCrew, many tool pages name the API as part of the product, like Stripe, described as payments and billing "in one dashboard and one API."
An API is built for a developer, who reads the documentation, picks the endpoints, writes the code, and handles sign-in, data formats, and errors. A 2025 study of MCP by Hou and colleagues on arXiv describes the time before MCP this way: developers "had to establish manual API connections for each tool or service." ZeroCrew's coding agents page lists the agents that now write much of that code for founders.
What is MCP?
MCP, the Model Context Protocol, is an open standard that lets an AI app connect to outside tools and data in one shared way. The MCP specification says the protocol uses JSON-RPC 2.0 messages between hosts (the AI apps), clients (connectors inside them), and servers (each tool's side). ZeroCrew's guide What is MCP? shows how founders connect agents to tools like Stripe and Gmail through MCP.
An MCP server is a menu an AI agent reads before the agent acts. In the current MCP specification, dated July 28, 2026, a client sends a tools/list request, and each tool comes back with a name, a plain-language description, and a JSON Schema for its inputs. ZeroCrew's own public MCP server works this way: its search_tools tool tells an agent to use it "when someone needs a tool for a job."
MCP belongs to the whole industry now, not one company. On December 9, 2025, the Linux Foundation announced the Agentic AI Foundation with MCP as a founding project, and counted more than 10,000 published MCP servers and support in Claude, Cursor, Microsoft Copilot, Gemini, VS Code, and ChatGPT. ZeroCrew marks each business tool in its directory that has joined that ecosystem with an MCP badge.
What is the difference between MCP and an API?
The main difference between MCP and an API is who does the reading. With an API, a developer reads the docs and writes code for each call ahead of time. With MCP, the AI agent reads the tool's menu at runtime and picks the action. ZeroCrew shows that split on every tool page, where an MCP badge marks a tool your agent can use on its own.
ZeroCrew compares the two side by side for founders who build with agents:
| API | MCP | |
|---|---|---|
| Built for | Developers writing code | AI agents and the apps they run in |
| How actions are found | Read the docs, write each call | The agent asks the server with tools/list |
| Who decides what runs | The code you wrote | The agent, with your approval |
| Reuse across AI apps | A new integration for each app | One server works in any app that supports MCP |
| Setup | API keys, code, and error handling | Usually add the server address and sign in |
| Best for | Fixed, repeatable steps in your product | Varied work an agent plans |
Both MCP and APIs need care with access. The MCP specification says hosts must get explicit user consent before invoking any tool, and that a human should be able to deny tool calls. An API key gives code whatever access the key allows. ZeroCrew's Stripe page notes that Stripe asks you to confirm actions such as refunds before its MCP server runs them.
Does MCP replace APIs?
MCP does not replace APIs. An MCP server gives agents a menu, and the actions on that menu often call the tool's existing API underneath. On ZeroCrew, tools like Stripe and Supabase offer both: Stripe has one API for payments, and Supabase generates REST and GraphQL APIs for each project, while each also runs an MCP server for your agents.
The API is the engine, and MCP is the dashboard an agent can drive. Your app's checkout calls Stripe's API in code, the same way every time. Your finance agent, asking which customers paid last week, uses Stripe's MCP server instead. ZeroCrew's payments page shows which payment tools, like Stripe and Paddle, offer an MCP server today.
When should a founder use an API, and when MCP?
A founder uses an API when the same step must run the same way every time, and MCP when an agent should decide the steps. ZeroCrew's MCP servers list marks every tool your agents can use, so you can see which side of that line a tool supports before you build anything:
- Use an API when your product makes the call: a checkout, a welcome email, a nightly sync. Code is predictable and testable.
- Use MCP when the work changes each time: answering a question about revenue, drafting replies, or updating a CRM after a call.
- Use both when your product serves agents: your own code keeps calling the API, while agents reach the same tool through MCP.
- Use a no-code tool when you want neither code nor an agent in the loop: Zapier and Make connect thousands of apps through their APIs for you.
How do you connect a tool through MCP or an API?
Connecting a tool through MCP can take a few minutes in an AI app, while connecting through an API takes code or an automation tool. ZeroCrew lists at least two options for each step below, so you can choose by price, by how much code you want to write, and by the tools you already use:
- Pick the AI app your agent runs in. Claude and ChatGPT both connect to your other apps; pick the one you already use. For code, Claude Code edits your codebase and runs commands, and Cursor is a code editor with agents built in.
- Find a tool with an MCP server. Browse MCP servers on ZeroCrew, then open a tool's page: Stripe or Paddle for payments, Supabase for your database, or Vercel for hosting.
- Add the server address and sign in. Paste the hosted MCP server address into your AI app's connector settings, or run the tool's local MCP server when it offers one. Stripe, Supabase, and Make connect with OAuth, according to their ZeroCrew pages.
- Start read-only. Ask questions first, approve each action, and give the agent more freedom once you trust its results. Stripe asks you to confirm actions such as refunds, and n8n lets you add human approval steps to an agent's workflow.
- Reach an API without MCP. Zapier or Make if you want no code, n8n if you want open source you can self-host, or Claude Code and Cursor to write the integration code for you.
Is MCP safe to use with your business data?
MCP is as safe as the access you grant and the servers you trust. The MCP specification says tools represent arbitrary code execution, that hosts must get consent before invoking any tool, and that descriptions of tool behavior, such as annotations, should be treated as untrusted unless they come from a trusted server. ZeroCrew links a tool's hosted MCP server, when it has one, from the tool's own page, next to its maker's site.
Researchers who mapped MCP security risks recommend least-privilege configuration for MCP servers, so a server gets only the access its job needs. Hou and colleagues (arXiv, 2025) also recommend version pinning and signature checks for MCP server code. A founder following ZeroCrew's What is MCP? guide lets an agent read first, then draft, and acts only after watching it work.
How does ZeroCrew help you choose between MCP and API tools?
ZeroCrew helps founders find the tools an agent can use today, with less time spent testing. ZeroCrew's MCP servers list shows 131 tools with an MCP server across 11 roles, as of November 2026, grouped by role. Each ZeroCrew tool page says what the tool's MCP server lets your agent do, how you connect, and which alternatives do the same job.
Your AI agent can search the ZeroCrew directory for you. ZeroCrew runs a public, read-only MCP server at https://zerocrew.ai/api/mcp/public with four tools: search_tools, get_tool, list_roles, and list_job. Add the ZeroCrew server as a custom connector in your AI app, ask which tool fits a job, and filter for tools that have an MCP server.
ZeroCrew's engineering tools sort 37 coding agents and apps into four jobs, as of November 2026: coding agents, app builders, backend and hosting, and AI models. ZeroCrew's backend and hosting page compares services like Supabase, Convex, and Vercel, each with an MCP server your agents can use.
What should a founder do first?
Start with one tool your company already pays for, and connect its MCP server to the AI app you use most. Ask your agent one real question from your week and watch what it does. ZeroCrew's directory shows the next tool to add, for every job a company of one needs done.