CLIs do work on mobile when they are packaged in skills that run in an appropriate VM behind the LLM.

Claude on the web does this. The only issue is controlling network access, which could be fixed by per-skill ACLs.

Walk me through how a user installs and then uses these CLIs from their mobile phone.

Create a skill that has the CLI in the scripts sub-directory. The implementation language depends on the LLM and the VM it uses. Claude includes shell, python, and a bunch of other interpreters in a Linux environment.

A skill's instructions can direct the LLM to call the CLI.

Claude skills can be installed into Claude web from a web browser. Those skills can then run on the Claude app on your phone.

Ok, I can see there's a new (to me) Customize section where you can install skills. You have been able to connect MCP servers for quite a while.

The UX here isn't great, but let's assume it can be improved. How would auth work with this alternative method? I want to connect to Puma store and that's done using a skill with a CLI. Can the CLI launch your web browser to do oauth from the skill (on a phone)? And then the credentials are saved where?

Not challenging you, I'm open to alternatives to MCP for sure. But MCP seems way more mature especially for non-programming use-cases.