Courier CLI

The official CLI for the Courier REST API.

It is generated with Stainless.

Installation

Installing with Homebrew

brew install trycourier/courier/courier

Installing with Go

To test or install the CLI locally, you need Go version 1.22 or later installed.

go install 'github.com/trycourier/courier-cli/cmd/courier@latest'

Once you have run go install, the binary is placed in your Go bin directory:

• Default location: $HOME/go/bin (or $GOPATH/bin if GOPATH is set)
• Check your path: Run go env GOPATH to see the base directory

If commands aren't found after installation, add the Go bin directory to your PATH:

# Add to your shell profile (.zshrc, .bashrc, etc.)
export PATH="$PATH:$(go env GOPATH)/bin"

Running Locally

After cloning the git repository for this project, you can use the scripts/run script to run the tool locally:

./scripts/run args...

Usage

The CLI follows a resource-based command structure:

courier [resource] <command> [flags...]

courier send message \
  --api-key 'My API Key' \
  --message '{}'

For details about specific commands, use the --help flag.

Environment variables

Environment variable	Required
COURIER_API_KEY	yes

Global flags

• --api-key (can also be set with COURIER_API_KEY env var)
• --help - Show command line usage
• --debug - Enable debug logging (includes HTTP request/response details)
• --version, -v - Show the CLI version
• --base-url - Use a custom API backend URL
• --format - Change the output format (auto, explore, json, jsonl, pretty, raw, yaml)
• --format-error - Change the output format for errors (auto, explore, json, jsonl, pretty, raw, yaml)
• --transform - Transform the data output using GJSON syntax
• --transform-error - Transform the error output using GJSON syntax

Passing files as arguments

To pass files to your API, you can use the @myfile.ext syntax:

courier <command> --arg @abe.jpg

Files can also be passed inside JSON or YAML blobs:

courier <command> --arg '{image: "@abe.jpg"}'
# Equivalent:
courier <command> <<YAML
arg:
  image: "@abe.jpg"
YAML

If you need to pass a string literal that begins with an @ sign, you can escape the @ sign to avoid accidentally passing a file.

courier <command> --username '\@abe'

Explicit encoding

For JSON endpoints, the CLI tool does filetype sniffing to determine whether the file contents should be sent as a string literal (for plain text files) or as a base64-encoded string literal (for binary files). If you need to explicitly send the file as either plain text or base64-encoded data, you can use @file://myfile.txt (for string encoding) or @data://myfile.dat (for base64-encoding). Note that absolute paths will begin with @file:// or @data://, followed by a third / (for example, @file:///tmp/file.txt).

courier <command> --arg @data://file.txt

Use with AI agents

The CLI works as a tool backend for AI coding agents. Because every API endpoint maps to a single shell command with structured JSON output, agents can call Courier without an SDK or custom integration.

export COURIER_API_KEY=your_api_key

# Send a message
courier send message \
  --message.to.user_id "user-123" \
  --message.template "order-confirmation" \
  --message.data '{"orderId": "ORD-456"}'

# Check delivery status
courier messages list --recipient "user-123" --format json

For richer agent integration, Courier also provides an MCP server that exposes the full API as structured tools for Cursor, Claude Code, Windsurf, and other MCP-compatible clients.

See Build with AI for setup instructions.