CLI

Run it

There is nothing to install for a one-off: npx @trylath/cli fetches and runs it. Installed, the binary is lath.With no arguments it prints the whole command list — every operation, with the sentence describing what it does.

npx @trylath/cli --help
# or
npm i -g @trylath/cli && lath --help

Store a key

lath init writes the key to ~/.lath/config.json with mode 600, so it is not passed on every command and does not land in your shell history.LATH_API_KEY overrides the file, which is what CI should use — an empty value counts as unset, because a template that exports LATH_API_KEY="" is more common than one that unsets it. LATH_BASE_URL and LATH_CONFIG_DIR override the rest.Without a key you get no_key and the fix, not a stack trace.

lath init --key lath_live_...

# CI, or a shell you do not want to persist anything in
LATH_API_KEY=lath_live_... lath email send --to you@example.com --subject Hi --text Hello

Call an operation

The shape is lath <product> <name...> with one flag per field. --json takes the whole input at once, which is easier to generate and easier to paste from the reference.A field the registry declares as an array is repeatable: pass the flag more than once.Anything not retry-safe takes --idempotency-key, and the CLI tells you which those are.

lath email send --to you@example.com --subject "Hello" --text "First one."

# the same call, as one object
lath email send --json '{"to":"you@example.com","subject":"Hello","text":"First one."}'

# a write that must not double-send if the job is retried
lath email send --json '{...}' --idempotency-key order-1043-receipt

Ask the CLI instead of the docs

--help on any command prints that operation’s fields with their types, which are required, and any enum values — plus the three facts you need before calling it: whether it reads or writes, whether retrying is safe, and the permission the key must have.This is generated from the registry, so it is never out of date with the API in the way a written page can be.

$ lath email send --help
lath email send

Sends one transactional email to one recipient, from the project's default sender...

mutation · not retry-safe: pass --idempotency-key · permission email:write

  --to                   string (required)  One recipient
  --template             string  A template name; provide variables with it
  --subject              string  Inline send: the subject
  --layout               string one of brand|none

Errors, and exit codes

A refusal prints the code and message on stderr, then the fix on its own line after an arrow. The exit code is non-zero, so a CI step fails rather than continuing quietly.The code is the same string the REST and MCP surfaces return, so a script can branch on it without parsing prose.

$ LATH_API_KEY= lath email send --to you@example.com --subject Hi --text Hello
no_key: No API key is configured.
→ Run `lath init` and paste a key, or set LATH_API_KEY.

An MCP server for a local agent

lath mcp runs an MCP server over stdio, which is how you attach a local agent that does not speak HTTP MCP — it uses the key the CLI already has, so there is no second credential to configure.The hosted endpoint is the other option and needs no install: POST https://platform.trylath.com/mcp.

{
  "mcpServers": {
    "lath": { "command": "npx", "args": ["-y", "@trylath/cli", "mcp"] }
  }
}

Overview

Get started

Frameworks

Sending

Platform

Surfaces