Oh My Posh Validator

What it does

Oh My Posh Validator is a hosted MCP endpoint run by the oh-my-posh project at ohmyposh.dev. You hand it the text of a prompt theme, in JSON, YAML or TOML, and it reports whether the theme matches the official oh-my-posh schema. Each error comes with the path of the property at fault, the schema keyword that failed and the offending value, so an assistant can point to the exact line to fix. It also adds warnings, such as a missing $schema property or an outdated version number, and returns the parsed configuration.

The endpoint has two tools, while the documentation page describes only validate_config. The second, validate_segment, checks one prompt segment on its own: it first insists the snippet is an object with a type and a style, then places it inside a minimal theme and reports only the errors that belong to the segment (website/api/mcp/index.js and website/api/shared/validator.js).

The format is detected automatically unless you pass format as json, yaml or toml. Nothing is installed: you add the address to your client and ask it to check a theme you paste or have open.

What it needs

An MCP client that can connect to a remote server over streamable HTTP. No account, key or oh-my-posh installation is needed; the endpoint takes anonymous requests. Your theme has to be passed in as text, since the server cannot open files on your machine.

Limits

It only validates: it does not create, edit or apply themes, and it cannot read your config file, so the content must be pasted or sent by the client. Its docs say it checks against the schema from the main branch, so a theme written for an older oh-my-posh release may get errors for properties that release does not have, and newly added properties may be accepted before your installed version supports them. A text that does not parse as JSON, YAML or TOML returns a parse error rather than schema findings. validate_segment stops at a missing type or style and skips the schema check until both are present.

Who it suits

Suits anyone editing an oh-my-posh theme with an assistant who wants a schema check before reloading the shell, with no install and no sign-in. It is read-only, and its docs say theme content is not kept. Pick something else if you want the assistant to write or change the theme file itself, or if you need checks that work offline or without sending your theme to a third-party host; pointing your editor at the schema URL through the theme's $schema property, as the server's own warning suggests, keeps the check local.