Marketing Automation · Integration
Customer.io
Add Customer.io to your product for your customers, and give your AI agents governed access to it.
Customer.io is driven by events rather than by lists, which changes what a good integration looks like. You identify a person, then send the things they did, and segments fall out of that rather than being maintained by hand. That means the integration worth building is usually the event path, not a nightly contact export, and it means ordering matters: an event that arrives before the person it belongs to is a support ticket waiting to happen. There are two APIs with different jobs, one for tracking and one for everything else, and pointing at the wrong one is the most common early mistake. fastn keeps each customer's workspace credentials scoped to them and absorbs the API changes.
In your product
Embedded for your customers. Per-tenant auth, no per-customer code, maintained by fastn.
Let a customer connect their own Customer.io workspace so lifecycle messaging follows what users actually do in your product.
Identify people and send product events, so segments stay current without anyone maintaining a list.
Trigger a campaign or broadcast from a product event rather than from a scheduled export.
Read campaign and delivery results back per tenant, so your product can act on what happened.
For your AI agents
Governed, audited access for the agents you build, through the MCP server.
An agent inspects which segments a person belongs to before suggesting a message.
An agent enrols a person in a campaign within governed permissions, with the action audited per tenant.
An agent reads delivery and engagement results and reports which journeys are underperforming.
Example prompt
Which campaigns did this customer receive in the last month, and which ones did they open?
Set up Customer.io in 4 steps
- 01Enable the Customer.io connector from your fastn dashboard.
- 02Have each customer authorise their own Customer.io account, so calls run under their credentials rather than a shared key.
- 03Decide which campaigns, segments and subscribers your product needs, map those fields, then enable the actions and triggers you want.
- 04Call it from your product and expose it to your agents through the same governed connection.
Why teams use the Customer.io integration
What you get by embedding it with fastn instead of building it yourself.
- Ship a Customer.io integration without building it. Your customers connect their own Customer.io account inside your product and work their campaigns, segments and subscribers there, with no per-customer code on your side.
- Handle the part that actually costs time: engagement data arrives as a high-volume event stream, so ordering and deduplication matter. fastn owns the auth, token refresh, rate limits, pagination and breaking-change fixes, so a Customer.io update is not your on-call problem.
- One integration serves your product and your agents. The same governed Customer.io connection powers in-product features and gives AI agents scoped, audited access, so you trigger and measure campaigns from inside your product without wiring it twice.
Used by these teams
Compare with
Braze
Iterable
MailchimpOften used alongside
Tools the same teams tend to run next to Customer.io, across other categories.
Salesforce
HubSpot
Pipedrive
Zoho CRMCustomer.io integration FAQ
How do I add a Customer.io integration to my product?
Enable the Customer.io connector in your fastn dashboard, then let each customer authenticate their own Customer.io account. fastn handles the OAuth flow, token storage and refresh per tenant, so there is no Customer.io client code in your app and no per-customer branch in your codebase. Setup is 4 steps.
Do my customers each connect their own Customer.io account?
Yes. Every connection is scoped to the individual customer, so each authorises their own Customer.io account and only ever sees their own campaigns, segments and subscribers. That per-tenant isolation is the point of an embedded integration: you support the long tail of customer setups without maintaining an integration per customer.
Can AI agents use this Customer.io integration?
Yes. The same connection is exposed to your agents through the fastn MCP gateway, with permissions scoped per tenant and every call audited. An agent inspects which segments a person belongs to before suggesting a message.
Who maintains the Customer.io integration?
fastn does. When Customer.io changes an endpoint, deprecates a field or alters its auth, the fix lands in the connector rather than in your backlog, and your customers' connections keep working.
Can I trigger a Customer.io campaign from an event in my product?
Yes. Product events can start a campaign, add a contact to a segment, or enrol someone in a journey, so lifecycle messaging follows what a user actually did rather than a nightly export.
Can I read engagement results back from Customer.io?
Yes. Results come back scoped per tenant, so your product can act on them without one customer's data mixing with another's. What you get depends on the channel: opens, clicks, bounces and unsubscribes where there are sends, and impressions, spend and conversions where there are campaigns.
What can I build with the Customer.io integration?
A common starting point: let a customer connect their own Customer.io workspace so lifecycle messaging follows what users actually do in your product. Teams also use it for the other use cases listed above, and expose it to agents for governed reads and writes.
How much does the Customer.io integration cost?
It is included. Pricing is based on connected accounts, not on how many connectors you enable, so adding Customer.io does not change your per-connector cost. You can start free with 3 connected accounts.
Add Customer.io to your product
Start free with 3 connected accounts. No sales call required, and no per-customer integration code.