Local vs remote servers, and authentication

The local-versus-remote choice shapes distribution, security, and auth. Here is how to decide and what authentication looks like for each.

Local servers #

A local server runs on the user's machine over stdio. It is private by default, needs no network auth, and reads any credentials from its environment. The tradeoff is distribution: every user installs and configures it themselves.

Remote servers #

A remote server is hosted once and reached over Streamable HTTP by many users. It is easy to distribute and update centrally, but now it is a network service that must authenticate and authorize each caller.

Authorization with OAuth 2.1 #

MCP's authorization model for remote servers is built on OAuth 2.1. The client obtains an access token through a standard OAuth flow and presents it on each request; the server validates it. This means a remote server can safely act on behalf of a specific user without ever seeing their password, and tokens can be scoped and revoked.