canonical: https://jentic.com/apis/convertkit.com/convertkit

# ConvertKit (Kit) API V3

ConvertKit is now Kit, and this entry covers the legacy V3 API, which Kit documents as deprecated and no longer in active development while keeping it available for use. Kit's own machine-readable specification covers V4 only, so this V3 specification is written and maintained by Jentic from Kit's V3 reference. Manage email subscribers, tag-based segmentation, automated sequences, broadcast emails, and purchase tracking for creator-focused businesses. Supports 32 endpoints covering subscriber lifecycle management, form integrations, tag-based organization, multi-step email sequences, broadcast scheduling and analytics, custom field management, and webhook-driven automation triggers.

## For AI agents

Manage email subscribers, trigger tag-based automations, send broadcasts, and track purchases for creator businesses. Covers 32 endpoints across subscribers, forms, sequences, tags, broadcasts, and webhooks.

## Scope

Does not handle payment processing, landing page hosting, or CRM deal tracking - use for email subscriber management, sequence automation, and broadcast delivery only.

## Capabilities

- Subscribe contacts to forms and sequences with custom field data and tag assignments in a single call
- Organize subscribers using tag-based segmentation, with per-tag subscriber lists from GET `/tags/{tag_id}/subscriptions` and tag-triggered automations
- Schedule and track broadcast emails with per-broadcast open and click statistics
- Build multi-step email sequences with subscriber-level enrollment and progress tracking
- Record purchases with product details and revenue for purchase-based automation triggers
- Register webhook automations triggered by subscriber events like form sign-ups and tag additions

## Use cases

### AI Agent Creator Email Automation

AI agents use the ConvertKit API through Jentic to manage subscriber lifecycles for creator businesses - course sellers, newsletter writers, and digital product vendors. The agent searches for 'add subscriber to email sequence' via Jentic, receives the POST `/sequences/{sequence_id}/subscribe` operation schema, and enrolls contacts in drip sequences without manual configuration.

Example prompt: Subscribe user@example.com to sequence ID 123 with first_name 'Alex' and tag them as 'course-buyer', then verify the subscription was created

### Tag-Based Subscriber Segmentation

Apply and remove tags on subscribers via `/tags/{tag_id}/subscribe` and `/tags/{tag_id}/unsubscribe` to drive segmentation and automation triggers. Tags act as the primary organization mechanism in ConvertKit - automations fire when tags are added, GET `/tags/{tag_id}/subscriptions` lists the subscribers carrying a tag, and POST `/sequences/{sequence_id}/subscribe` can apply tags as it enrolls someone. Each call applies or removes one tag for one subscriber, so a re-segmentation pass iterates the list.

Example prompt: Tag all subscribers from form ID 456 with 'webinar-attendee' and retrieve the updated subscriber list for that tag

### Broadcast Email Campaigns

Create and manage broadcast emails via POST /broadcasts, which takes a subject, the email content, and optional description, public, published_at, send_at, email_address, thumbnail_alt and thumbnail_url fields. Each broadcast tracks delivery statistics at `/broadcasts/{id}/stats` including recipient count, open rate, click rate, unsubscribe count, total clicks, status, and send progress. Leaving send_at blank creates a draft; setting it to a future time schedules the send.

Example prompt: Create a broadcast with subject 'New Course Launch' and its HTML content scheduled with send_at, then retrieve its delivery stats from GET `/broadcasts/{id}/stats` after it sends

### Purchase Tracking and Revenue Attribution

Record customer purchases via POST /purchases with product details, transaction amounts, and subscriber association. Purchase data drives revenue-based automations and lifetime value calculations within ConvertKit. The GET /purchases endpoint retrieves purchase history for reporting, while individual purchase records link transactions to specific subscribers for targeted post-purchase sequences.

Example prompt: Record a $97 purchase of product 'Email Marketing Course' for subscriber ID 789 and verify the purchase appears in their profile

## Key endpoints

| Method | Path | Description |
| --- | --- | --- |
| POST | `/forms/{form_id}/subscribe` | Subscribe a contact to a form |
| GET | `/subscribers` | List all subscribers |
| POST | `/tags/{tag_id}/subscribe` | Tag a subscriber |
| POST | `/sequences/{sequence_id}/subscribe` | Add subscriber to a sequence |
| GET | `/broadcasts` | List all broadcasts |
| GET | `/broadcasts/{id}/stats` | Get broadcast statistics |
| POST | `/purchases` | Record a purchase |
| POST | `/automations/hooks` | Register an automation webhook |

## Key resources

- **Subscribers** — Manage subscriber profiles, custom fields, tags, and subscription status
- **Forms** — Subscribe contacts to forms and retrieve form subscription lists
- **Sequences** — Enroll subscribers in multi-step email drip sequences
- **Tags** — Apply and remove tags for subscriber segmentation and automation triggers
- **Broadcasts** — Create and track one-time email sends with delivery statistics
- **Purchases** — Record transactions for revenue tracking and purchase-based automations
- **Webhooks** — Register automation hooks triggered by subscriber events

## Why Jentic

- **Setup:** Wiring ConvertKit by hand means tracking which of the two V3 query-parameter credentials each call needs, api_key or the privileged api_secret, and wiring the subscribe, tag, and broadcast calls yourself. Through Jentic you install once, import the ConvertKit (Kit) API from the API Directory, store the credentials once, and your agent calls it.
- **Permission scoping:** ConvertKit puts the form, tag, and sequence ids in the URL path (`/forms/{form_id}/subscribe`, `/tags/{tag_id}/subscribe`, `/sequences/{sequence_id}/subscribe`), so a rule can pin your agent to one form, tag, or sequence: it can subscribe people there and nothing else. You choose the operations it may call, so purchases or automation hooks are not included unless you add them.
- **Credential handling:** Your ConvertKit API key and secret are stored once, encrypted, by your own Jentic One instance and injected at execution time. They never enter the agent's prompt, logs, or context.
- **Discovery method:** Agents search Jentic by intent such as 'subscribe a user to an email sequence' or 'list recent broadcasts', and Jentic returns the matching ConvertKit operation with its input schema so the agent calls the right endpoint without browsing the reference docs.

## Related APIs

- **Mailchimp Marketing API** — Full-featured email marketing platform with audience management, templates, and e-commerce integrations
- **Klaviyo API** — E-commerce-focused marketing automation with predictive analytics and behavioral event tracking
- **Constant Contact API** — Email marketing for small businesses with event management and social media posting
- **Stripe API** — Payment processing that feeds purchase events into ConvertKit for revenue-triggered automations

## FAQ

### Which OpenAPI specification does this ConvertKit (Kit) API V3 entry use?

Kit publishes one OpenAPI document, for API V4, and lists it at developers.kit.com/api-reference/v4.json. That document describes the V4 surface on api.kit.com, not the V3 surface this entry covers, and the V3 reference at developers.kit.com/api-reference/v3 is prose only. So the specification here is a curated V3 specification written and maintained by Jentic from that reference, not a copy of Kit's V4 document. Kit's own recommendation is to use API V4 for all new projects, which means the api.kit.com/v4 surface rather than the V3 surface here.

### What authentication does the ConvertKit API V3 use?

Two credentials, and they are alternatives rather than a pair: Kit's V3 documentation states that all calls accept an api_key query parameter, that some calls require the privileged api_secret query parameter instead, and that there is no need to send both. api_secret is the one marked required on most operations, including reads such as GET /account, GET /subscribers, GET /broadcasts and GET /purchases, while api_key alone covers GET /forms, GET /tags, GET /sequences, POST `/forms/{form_id}/subscribe` and POST `/sequences/{sequence_id}/subscribe.` Through Jentic your ConvertKit credentials are stored encrypted by your own Jentic One instance and injected at call time, so raw keys never enter the agent context.

### Can I add subscribers to sequences with the ConvertKit API?

Yes. POST to `/sequences/{sequence_id}/subscribe` with the subscriber's email address and optional fields (first_name, custom fields, tags). The subscriber receives the sequence emails starting from step one. Check enrollment via GET `/sequences/{sequence_id}/subscriptions.`

### What are the rate limits for the ConvertKit API V3?

Kit's V3 documentation states a limit of no more than 120 requests over a rolling 60 second period for a given API key. Requests over that limit receive a 429 status code, and Kit recommends spacing requests out and backing off exponentially. V3 has no batch or bulk endpoints, so a large import is one call per subscriber inside that window.

### How do I tag subscribers to trigger automations through Jentic?

Search Jentic for 'tag a subscriber for automation' to find the POST `/tags/{tag_id}/subscribe` operation. Provide the subscriber email and the operation adds the tag, which can trigger any automation rule configured for that tag in ConvertKit.

### Can I track broadcast performance with the ConvertKit API?

Yes. Kit's V3 reference documents GET `/broadcasts/{id}/stats` as returning recipient count, open rate, click rate, unsubscribe count, total clicks, status, and send progress for one broadcast. GET /broadcasts lists your broadcasts with their id and subject, so an agent lists first and then queries stats per broadcast id for engagement analysis.

### How do I set up webhook automations via the ConvertKit API?

POST to `/automations/hooks` with a target_url and event object specifying the trigger (e.g., subscriber.form_subscribe, subscriber.tag_add). ConvertKit sends a POST to your URL whenever the event fires. V3 has no list operation for hooks, so keep the returned id and remove a hook with DELETE `/automations/hooks/{id}.`

### Is there a ConvertKit (Kit) MCP server?

Yes. Kit offers an official remote MCP server, documented at developers.kit.com/mcp/kit-mcp, which Kit describes as a one-to-one mapping of its V4 API surface and which is available on its paid plans. You can also connect this API directly through Jentic: your agent gets the full 32-endpoint V3 surface from the specification, without loading another server's tool definitions into its context, your ConvertKit credential is injected at call time by your self-hosted instance instead of living in an MCP client config, and your own rules decide which operations the agent may call.

### Can I limit what my agent is allowed to do with the ConvertKit (Kit) API V3?

Yes. Because you run Jentic One yourself, your own rules decide which ConvertKit operations and credentials the agent may use. ConvertKit puts the form, tag, and sequence ids in the URL path (`/forms/{form_id}/subscribe`, `/tags/{tag_id}/subscribe`, `/sequences/{sequence_id}/subscribe`), so a rule can pin the agent to a single form, tag, or sequence and let it subscribe people there and nothing else. You also choose the operations it can call, so purchase recording (POST /purchases) and automation hooks (POST `/automations/hooks`) stay off limits unless you add them.