CLI

The package installs an email-builder command. It reads a document as JSON from a file or stdin and prints JSON to stdout, so any language can use it.

npx email-builder <command> [file]

render

Renders a document to HTML and plain text.

npx email-builder render design.json
cat design.json | npx email-builder render

{ "html": "<!DOCTYPE html>…", "text": "…", "warnings": [] }

If the document is invalid, it prints { "ok": false, "issues": [...] } and exits with code 1.

validate

Validates a document and lints it.

npx email-builder validate design.json

{ "ok": true, "issues": [], "warnings": [{ "code": "missing-preheader", "severity": "info", "message": "…" }] }

Exits with 1 when the document is invalid. Lint warnings don't affect the exit code.

mcp

Runs the MCP server over stdio.

npx email-builder mcp --dir ./emails

Option	Default	Description
--dir <folder>	current folder	Where the email files live
--assets-url <url>	jsDelivr	Where rendered social icons load from
--brief <text>	–	Brand, audience or tone guidance added to the instructions
--merge-tags <a,b,…>	–	Merge tags your sending platform supports; the AI uses only these
--blocks <module>	–	JS module exporting custom blocks (default export or customBlocks)
--require-unsubscribe	off	check_email and render_email warn when there's no {{ unsubscribe_url }}

Exit codes

Running email-builder with no command, or with --help, prints the usage to stderr and exits with 0.

Code	Meaning
0	Success
1	The document is invalid
2	Unknown command, the input isn't JSON, or mcp couldn't start (e.g. the --blocks module didn't load or doesn't export an array)