feat: add marketing tools registry for agent discovery

Create centralized tools/ directory with REGISTRY.md index and 29
integration guides covering analytics, SEO, CRM, payments, referral,
email, ads, automation, and commerce platforms.

Each guide includes API endpoints, authentication, common operations,
and links to relevant skills. Updated AGENTS.md and key skills
(referral-program, analytics-tracking, email-sequence, paid-ads)
with tool integration references.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tools/integrations/kit.md

@@ -0,0 +1,167 @@
+# Kit (formerly ConvertKit)
+
+Email marketing platform for creators and newsletter businesses.
+
+## Capabilities
+
+| Integration | Available | Notes |
+|-------------|-----------|-------|
+| API | ✓ | REST API for subscribers, forms, sequences |
+| MCP | - | Not available |
+| CLI | - | Not available |
+| SDK | ✓ | JavaScript, Ruby gems available |
+
+## Authentication
+
+- **Type**: API Key or API Secret
+- **Parameter**: `api_key={key}` or `api_secret={secret}` in query/body
+- **Get key**: Settings > Advanced in Kit dashboard
+
+## Common Agent Operations
+
+### List subscribers
+
+```bash
+GET https://api.convertkit.com/v3/subscribers?api_secret={api_secret}&page=1
+
+```
+
+### Get subscriber
+
+```bash
+GET https://api.convertkit.com/v3/subscribers/{subscriber_id}?api_secret={api_secret}
+```
+
+### Add subscriber to form
+
+```bash
+POST https://api.convertkit.com/v3/forms/{form_id}/subscribe
+
+{
+  "api_key": "{api_key}",
+  "email": "user@example.com",
+  "first_name": "John",
+  "fields": {
+    "company": "Example Inc"
+  }
+}
+```
+
+### Add subscriber to sequence
+
+```bash
+POST https://api.convertkit.com/v3/sequences/{sequence_id}/subscribe
+
+{
+  "api_key": "{api_key}",
+  "email": "user@example.com"
+}
+```
+
+### Tag subscriber
+
+```bash
+POST https://api.convertkit.com/v3/tags/{tag_id}/subscribe
+
+{
+  "api_key": "{api_key}",
+  "email": "user@example.com"
+}
+```
+
+### Remove tag from subscriber
+
+```bash
+DELETE https://api.convertkit.com/v3/subscribers/{subscriber_id}/tags/{tag_id}?api_secret={api_secret}
+```
+
+### Update subscriber
+
+```bash
+PUT https://api.convertkit.com/v3/subscribers/{subscriber_id}
+
+{
+  "api_secret": "{api_secret}",
+  "first_name": "Jane",
+  "fields": {
+    "plan": "pro"
+  }
+}
+```
+
+### Unsubscribe
+
+```bash
+PUT https://api.convertkit.com/v3/unsubscribe
+
+{
+  "api_secret": "{api_secret}",
+  "email": "user@example.com"
+}
+```
+
+### List forms
+
+```bash
+GET https://api.convertkit.com/v3/forms?api_key={api_key}
+```
+
+### List sequences
+
+```bash
+GET https://api.convertkit.com/v3/sequences?api_key={api_key}
+```
+
+### List tags
+
+```bash
+GET https://api.convertkit.com/v3/tags?api_key={api_key}
+```
+
+### Create broadcast
+
+```bash
+POST https://api.convertkit.com/v3/broadcasts
+
+{
+  "api_secret": "{api_secret}",
+  "subject": "Newsletter Subject",
+  "content": "<p>Email content here</p>",
+  "email_layout_template": "default"
+}
+```
+
+## Key Concepts
+
+- **Subscribers** - Email contacts
+- **Forms** - Signup forms
+- **Sequences** - Automated email series
+- **Tags** - Subscriber labels
+- **Broadcasts** - One-time sends
+- **Custom Fields** - Subscriber attributes
+
+## Subscriber States
+
+- `active` - Can receive emails
+- `unsubscribed` - Opted out
+- `bounced` - Email bounced
+- `complained` - Marked as spam
+- `inactive` - Cold subscriber
+
+## When to Use
+
+- Creator/newsletter businesses
+- Simple email automation
+- Form-based list building
+- Tagging and segmentation
+- Course email sequences
+
+## Rate Limits
+
+- 120 requests per minute
+- Batch endpoints available
+
+## Relevant Skills
+
+- email-sequence
+- content-strategy