OIDC? Ease of deployment in a company?

You can have your IT department configure an MCP for the org, and your regular non-technical users click a button and login with their account the service. Then they get all the tool calls authenticated as themselves.

The AI probably can figure out. However, Claude Code and other tools are built to support MCP. This means MCP is probably more reliable than using REST API + llms.txt.

Standardization. Who writes llms.txt? Everyone writes their own? Will agents still behave the same?