ConvertKit (Kit) API V3
Agent-ready OpenAPI document · curated by JenticMarketingEmail MarketingapiKey32 EndpointsREST
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For 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.
Use for: I need to add a subscriber to a specific form, I want to tag a subscriber to trigger an automation, List all subscribers with a specific tag, Get the open rate statistics for a recent broadcast
Not supported: Does not handle payment processing, landing page hosting, or CRM deal tracking - use for email subscriber management, sequence automation, and broadcast delivery only.
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.
Install Jentic One Beta
Connect the ConvertKit (Kit) API V3 to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the ConvertKit (Kit) API V3, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
1
Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fconvertkit.com%2Fconvertkit" | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL "https://jentic.com/install.sh?src=apis&api=%2Fapis%2Fconvertkit.com%2Fconvertkit" | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with ConvertKit (Kit) API V3 API.
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
Patterns agents use ConvertKit (Kit) API V3 API for, with concrete tasks.
★ 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.
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.
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.
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.
Record a $97 purchase of product 'Email Marketing Course' for subscriber ID 789 and verify the purchase appears in their profile
Key Endpoints
32 endpoints — 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.
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
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
Why Jentic?
What agents get from Jentic-routed access to this vendor.
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 isolation
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.
Intent-based discovery
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
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using ConvertKit (Kit) API V3 API through Jentic.
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.
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