job.mackerl.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>Label</key>
        <string>job.mackerl</string>
        <key>ProgramArguments</key>
        <array>
                <string>/PATH_TO_MACKEREL_AGENT/mackerel-agent</string>
                <string>-conf=/Users/USER/Library/mackerel-agent/mackerel-agent.conf</string>
        </array>
        <key>RunAtLoad</key>
        <true/>
        <key>StandardErrorPath</key>
        <string>/Users/USER/Documents/stderr</string>
        <key>StandardOutPath</key>
        <string>/Users/USER/Documents/stdout</string>
        <key>WorkingDirectory</key>
        <string>/Users/USER/</string>
</dict>
</plist>

sudo launchctl load -w /Library/LaunchDaemons/job.mackerl.plist