Customer.io

Customer.io

This connector reads and sends with Customer.io Journeys (customer messaging) through the Customer.io App API with an App API key: people and their attributes, segments, activity and deliveries; automations (campaigns), broadcasts and one-time sends (newsletters) with their metrics; and it can send transactional email and trigger API broadcasts.

Setup (about 3 minutes)

1. In Customer.io open Settings, Account Settings, API Credentials, App API Keys (https://fly.customer.io/settings/api_credentials?keyType=app) and click Create App API Key. Pick the workspace and the access you want (full access, or read-only plus sending if you only want reads and sends).
2. Copy the key: it is shown once. Paste it into CUSTOMERIO_APP_API_KEY.
3. Set CUSTOMERIO_API_URL to your account's data center: https://api.customer.io for US accounts, https://api-eu.customer.io for EU accounts (the region is chosen when the account is created).

The App API key acts for its workspace, not for one person: whoever uses this connector sees every person, segment and message the key can read. Share the MCP server only with people allowed to see that.

The Track API (identify people, track events, delete people) uses a different credential (Site ID and Track API key, HTTP Basic, on track.customer.io) and is not part of this connector.

Limits: the App API allows about 10 requests per second; transactional sends share a soft limit of 3,000 requests per 3 seconds, and broadcast triggers are limited to one every 10 seconds. Customer.io answers 429 when a limit is reached. Lists come in pages: when next is in the answer, call the same tool again with start = next; when it is empty you have everything.

How to work

1. Check the key and the workspace: customer_io_list_workspaces.
2. Find people: customer_io_find_customers_by_email by email, or customer_io_search_customers with a segment or attribute filter (POST, but only reads). Then customer_io_get_customer_attributes, customer_io_get_customer_segments, customer_io_list_customer_activities and customer_io_list_customer_messages with that customer_id (id_type email, phone or cio_id when you only have those).
3. Audience: customer_io_list_segments, customer_io_get_segment, customer_io_get_segment_customer_count and customer_io_list_segment_members.
4. Automations: customer_io_list_campaigns, customer_io_get_campaign and customer_io_get_campaign_metrics (start and end as Unix timestamps).
5. Broadcasts and one-time sends: customer_io_list_broadcasts, customer_io_get_broadcast, customer_io_get_broadcast_metrics, customer_io_list_newsletters and customer_io_get_newsletter_metrics.
6. Deliveries and activity: customer_io_list_messages, customer_io_get_message, customer_io_list_activities.
7. Sending, each only after the user confirms: customer_io_send_transactional_email sends one email (find the template with customer_io_list_transactional_messages); show recipient, subject and content first. customer_io_trigger_broadcast sends to many people at once: show the broadcast and the audience size and wait for an explicit "yes, send". Follow it with customer_io_get_broadcast_trigger.

Timestamps are Unix seconds. Customer.io calls automations "campaigns" and one-time sends "newsletters" in the API.

Common errors

• 401 "unauthorized": the App API key is wrong or deleted, or it belongs to the other region; check CUSTOMERIO_API_URL (US or EU).
• 403: the key's access does not include this action (for example a read-only key used to send).
• 404: the id does not exist in this workspace.
• 400 / 422: a parameter or the filter is invalid; the errors list says which.
• 429: the rate limit is reached; wait and retry once.

Out of scope here: the Track API (identify, events, deletes), the Pipelines API, exports and imports, collections, snippets, reporting webhooks, ESP suppressions, object types, and changing automation or broadcast content.