Short answer
MCP is a connection protocol. Arc is auth for AI agents. Arc can use MCP as an adapter, but Arc's core job is identity, permissions, approvals, audit logs, and revocation.
Comparison
| Question | MCP | Arc |
|---|---|---|
| What is it? | A way for AI clients to connect to tools. | A way for apps to control agent actions. |
| Primary user | Agent clients and tool servers. | Apps, developers, users, and security teams. |
| Core decision | Which tools are available? | Should this agent action be allowed, ask, or blocked? |
| User control | Depends on implementation. | Built around permissions, approval, audit, and revocation. |
How they work together
If a client expects MCP, Arc can expose the approved action surface through an MCP-compatible path. The important part is that Arc enforces the user's permission grant before the app action runs.
Why this distinction matters
Teams can adopt a protocol and still lack a safe authorization model. Arc focuses on the authorization model: who is acting, which action is requested, what the user allowed, and how to audit or revoke it.