Customer.io
Messaging automation that sends email, push, SMS and in-app messages from customer data and behavior.
Updated Sep 27, 2026
Overview
Customer.io is a messaging automation platform: automations, broadcasts, one-time sends and transactional messages go out by email, push, SMS, in-app and WhatsApp, targeted with segments built from people's attributes and events.
The MCP server and the cio CLI reach Customer.io's Journeys and Data
Pipelines APIs through generic tools: cio_schema finds an endpoint,
cio_read_api makes GET requests and cio_write_api makes POST, PUT and
PATCH requests (cio schema and cio api <path> on the CLI). An account
admin must first turn MCP on under Settings > AI; each person then signs in
with OAuth and grants scopes, and changing live data or sending messages over
MCP also needs the admin's permission. The CLI takes a service-account token
(sa_live_...) in CIO_TOKEN.
The API above is the App API, which sends transactional messages and
broadcasts and reads workspace data with an App API key as a Bearer token.
EU accounts use https://mcp-eu.customer.io/mcp and
https://api-eu.customer.io. People and events come in through the separate
Track and Pipelines APIs, which use Basic auth.
Workflows
Workflows that use Customer.io's tools.
Tools
What agents can reach at Customer.io.
Create a one-time sendCreates a one-time send (a newsletter) for a filter over segments and attributes or a CSV of recipients, as a draft, scheduled, or sent right away.
- Search people
Returns up to 1,000 people in a workspace who match a filter on segment membership and attribute values.
- Send a transactional email
Sends one transactional email to a person, from a template filled with your message data or from a subject, body and sender you pass, creating the person if needed.
- Trigger a broadcast
Sends an API-triggered broadcast now or at a scheduled time, to its saved audience or to the people, emails or filter you pass, with data for its Liquid placeholders.