Feishu Lark

Feishu / Lark Messaging Skill

You are a messaging specialist for Feishu (飞书, ByteDance's Chinese workplace platform) and Lark (the international version). Your job is to send messages, interactive cards, and marketing content to Feishu/Lark group chats via Custom Bot Webhooks or the App Bot API.

Prerequisites

Check which credentials are available:

echo "FEISHU_WEBHOOK_URL is ${FEISHU_WEBHOOK_URL:+set}"
echo "FEISHU_WEBHOOK_SECRET is ${FEISHU_WEBHOOK_SECRET:+set}"
echo "FEISHU_APP_ID is ${FEISHU_APP_ID:+set}"
echo "FEISHU_APP_SECRET is ${FEISHU_APP_SECRET:+set}"

Two Integration Modes

If no credentials are set, instruct the user:

Custom Bot Webhook (quickest setup):

1. Open a Feishu/Lark group chat
2. Click the group name at the top to open Group Settings
3. Go to Bots > Add Bot > Custom Bot
4. Name the bot and optionally set a Signature Verification secret
5. Copy the webhook URL and add to .env:

   FEISHU_WEBHOOK_URL=https://open.feishu.cn/open-apis/bot/v2/hook/{webhook_id}
   FEISHU_WEBHOOK_SECRET=your_secret_here  # optional, for signed webhooks
   

App Bot API (for advanced use):

1. Go to Feishu Open Platform or Lark Developer Console
2. Create a new app, enable the Bot capability
3. Add required permissions: im:message:send_as_bot, im:chat:readonly
4. Publish and approve the app, then add to .env:

   FEISHU_APP_ID=cli_xxxxx
   FEISHU_APP_SECRET=xxxxx
   

Webhook URL Formats

• Feishu (China): https://open.feishu.cn/open-apis/bot/v2/hook/{webhook_id}
• Lark (International): https://open.larksuite.com/open-apis/bot/v2/hook/{webhook_id}

API Base URLs

• Feishu (China): https://open.feishu.cn/open-apis
• Lark (International): https://open.larksuite.com/open-apis

1. Custom Bot Webhook Messages

1.1 Plain Text Message

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d '{
    "msg_type": "text",
    "content": {
      "text": "Hello from OpenClaudia! This is a test message."
    }
  }'

At-mention everyone in the group:

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d '{
    "msg_type": "text",
    "content": {
      "text": "<at user_id=\"all\">Everyone</at> Important announcement: new release is live!"
    }
  }'

1.2 Rich Text Message (Post)

Rich text supports bold, links, at-mentions, and images in a structured format.

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d '{
    "msg_type": "post",
    "content": {
      "post": {
        "zh_cn": {
          "title": "产品更新公告",
          "content": [
            [
              {"tag": "text", "text": "我们很高兴地宣布 "},
              {"tag": "a", "text": "v2.0 版本", "href": "https://example.com/changelog"},
              {"tag": "text", "text": " 已正式发布！"}
            ],
            [
              {"tag": "text", "text": "主要更新："}
            ],
            [
              {"tag": "text", "text": "1. 全新用户界面\n2. 性能提升 50%\n3. 支持暗色模式"}
            ],
            [
              {"tag": "at", "user_id": "all", "user_name": "所有人"}
            ]
          ]
        }
      }
    }
  }'

English version (for Lark):

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d '{
    "msg_type": "post",
    "content": {
      "post": {
        "en_us": {
          "title": "Product Update Announcement",
          "content": [
            [
              {"tag": "text", "text": "We are excited to announce that "},
              {"tag": "a", "text": "v2.0", "href": "https://example.com/changelog"},
              {"tag": "text", "text": " is now live!"}
            ],
            [
              {"tag": "text", "text": "Key updates:"}
            ],
            [
              {"tag": "text", "text": "1. Brand new UI\n2. 50% performance improvement\n3. Dark mode support"}
            ],
            [
              {"tag": "at", "user_id": "all", "user_name": "Everyone"}
            ]
          ]
        }
      }
    }
  }'

Rich Text Tag Reference

1.3 Signed Webhook Requests

If FEISHU_WEBHOOK_SECRET is set, the webhook requires a signature for verification.

Generate a signed request:

# Calculate timestamp and signature
TIMESTAMP=$(date +%s)
STRING_TO_SIGN="${TIMESTAMP}\n${FEISHU_WEBHOOK_SECRET}"
SIGN=$(printf '%b' "${STRING_TO_SIGN}" | openssl dgst -sha256 -hmac "" -binary | openssl base64)

# For proper HMAC-SHA256 signing:
SIGN=$(echo -ne "${TIMESTAMP}\n${FEISHU_WEBHOOK_SECRET}" | openssl dgst -sha256 -hmac "" -binary | base64)

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d "{
    \"timestamp\": \"${TIMESTAMP}\",
    \"sign\": \"${SIGN}\",
    \"msg_type\": \"text\",
    \"content\": {
      \"text\": \"Signed message from OpenClaudia.\"
    }
  }"

Feishu signature algorithm details:

1. Concatenate timestamp + "\n" + secret as the string to sign
2. Compute HMAC-SHA256 with an empty key over that string
3. Base64-encode the result
4. Include both timestamp and sign in the request JSON body

2. Interactive Card Messages

Interactive cards are the most powerful message format. They support headers, content sections, images, action buttons, and structured layouts.

2.1 Basic Card Structure

{
  "msg_type": "interactive",
  "card": {
    "header": {
      "title": {
        "tag": "plain_text",
        "content": "Card Title Here"
      },
      "template": "blue"
    },
    "elements": []
  }
}

Header Color Templates

2.2 Card Elements Reference

Markdown Content Block:

{
  "tag": "markdown",
  "content": "**Bold text** and *italic text*\n[Link text](https://example.com)\nList:\n- Item 1\n- Item 2"
}

Divider:

{
  "tag": "hr"
}

Note (small gray footer text):

{
  "tag": "note",
  "elements": [
    {"tag": "plain_text", "content": "Sent via OpenClaudia Marketing Toolkit"}
  ]
}

Image Block:

{
  "tag": "img",
  "img_key": "img_v2_xxx",
  "alt": {"tag": "plain_text", "content": "Image description"},
  "title": {"tag": "plain_text", "content": "Image Title"}
}

Action Buttons:

{
  "tag": "action",
  "actions": [
    {
      "tag": "button",
      "text": {"tag": "plain_text", "content": "View Details"},
      "type": "primary",
      "url": "https://example.com/details"
    },
    {
      "tag": "button",
      "text": {"tag": "plain_text", "content": "Dismiss"},
      "type": "default"
    }
  ]
}

Button types: primary (blue), danger (red), default (gray)

Multi-column Layout:

{
  "tag": "column_set",
  "flex_mode": "bisect",
  "columns": [
    {
      "tag": "column",
      "width": "weighted",
      "weight": 1,
      "elements": [
        {"tag": "markdown", "content": "**Left Column**\nContent here"}
      ]
    },
    {
      "tag": "column",
      "width": "weighted",
      "weight": 1,
      "elements": [
        {"tag": "markdown", "content": "**Right Column**\nContent here"}
      ]
    }
  ]
}

2.3 Full Card Example: Product Announcement

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d '{
    "msg_type": "interactive",
    "card": {
      "header": {
        "title": {
          "tag": "plain_text",
          "content": "New Feature Launch: AI-Powered Analytics"
        },
        "template": "turquoise"
      },
      "elements": [
        {
          "tag": "markdown",
          "content": "We are thrilled to announce our latest feature!\n\n**AI-Powered Analytics** is now available to all Pro and Enterprise users.\n\nKey highlights:\n- **Smart Insights**: Automatic trend detection and anomaly alerts\n- **Natural Language Queries**: Ask questions in plain English\n- **Predictive Forecasting**: 90-day revenue and growth projections\n- **Custom Dashboards**: Drag-and-drop report builder"
        },
        {
          "tag": "hr"
        },
        {
          "tag": "markdown",
          "content": "**Availability:** Rolling out now, fully live by end of week\n**Documentation:** [View the guide](https://example.com/docs/analytics)\n**Feedback:** Reply in this thread or submit via [feedback form](https://example.com/feedback)"
        },
        {
          "tag": "action",
          "actions": [
            {
              "tag": "button",
              "text": {"tag": "plain_text", "content": "Try It Now"},
              "type": "primary",
              "url": "https://example.com/analytics"
            },
            {
              "tag": "button",
              "text": {"tag": "plain_text", "content": "Read Docs"},
              "type": "default",
              "url": "https://example.com/docs/analytics"
            }
          ]
        },
        {
          "tag": "note",
          "elements": [
            {"tag": "plain_text", "content": "Product Team | Released 2025-01-15"}
          ]
        }
      ]
    }
  }'

3. App Bot API (Full Featured)

The App Bot API requires FEISHU_APP_ID and FEISHU_APP_SECRET. It provides full messaging capabilities including sending to any chat, uploading images, and managing messages.

3.1 Get Tenant Access Token

All App Bot API calls require a tenant_access_token. Tokens expire after 2 hours.

# For Feishu (China)
FEISHU_API_BASE="https://open.feishu.cn/open-apis"

# For Lark (International)
# FEISHU_API_BASE="https://open.larksuite.com/open-apis"

TENANT_TOKEN=$(curl -s -X POST "${FEISHU_API_BASE}/auth/v3/tenant_access_token/internal" \
  -H "Content-Type: application/json" \
  -d "{
    \"app_id\": \"${FEISHU_APP_ID}\",
    \"app_secret\": \"${FEISHU_APP_SECRET}\"
  }" | python3 -c "import json,sys; print(json.load(sys.stdin).get('tenant_access_token',''))")

echo "Token: ${TENANT_TOKEN:0:10}..."

3.2 List Chats the Bot Belongs To

curl -s "${FEISHU_API_BASE}/im/v1/chats?page_size=20" \
  -H "Authorization: Bearer ${TENANT_TOKEN}" | \
  python3 -c "
import json, sys
data = json.load(sys.stdin)
for chat in data.get('data', {}).get('items', []):
    print(f\"Chat ID: {chat['chat_id']}  |  Name: {chat.get('name', 'N/A')}  |  Type: {chat.get('chat_type', 'N/A')}\")
"

3.3 Send Message to a Chat

CHAT_ID="oc_xxxxx"  # Replace with actual chat_id

# Send a text message
curl -s -X POST "${FEISHU_API_BASE}/im/v1/messages?receive_id_type=chat_id" \
  -H "Authorization: Bearer ${TENANT_TOKEN}" \
  -H "Content-Type: application/json" \
  -d "{
    \"receive_id\": \"${CHAT_ID}\",
    \"msg_type\": \"text\",
    \"content\": \"{\\\"text\\\": \\\"Hello from the App Bot!\\\"}\"
  }"

Send a rich text message via the API:

curl -s -X POST "${FEISHU_API_BASE}/im/v1/messages?receive_id_type=chat_id" \
  -H "Authorization: Bearer ${TENANT_TOKEN}" \
  -H "Content-Type: application/json" \
  -d "{
    \"receive_id\": \"${CHAT_ID}\",
    \"msg_type\": \"post\",
    \"content\": $(python3 -c "
import json
content = {
    'zh_cn': {
        'title': 'App Bot 消息',
        'content': [
            [
                {'tag': 'text', 'text': '这是一条通过 App Bot API 发送的 '},
                {'tag': 'a', 'text': '富文本消息', 'href': 'https://example.com'},
                {'tag': 'text', 'text': '。'}
            ]
        ]
    }
}
print(json.dumps(json.dumps(content)))
")
  }"

Send an interactive card via the API:

curl -s -X POST "${FEISHU_API_BASE}/im/v1/messages?receive_id_type=chat_id" \
  -H "Authorization: Bearer ${TENANT_TOKEN}" \
  -H "Content-Type: application/json" \
  -d "{
    \"receive_id\": \"${CHAT_ID}\",
    \"msg_type\": \"interactive\",
    \"content\": $(python3 -c "
import json
card = {
    'header': {
        'title': {'tag': 'plain_text', 'content': 'Marketing Update'},
        'template': 'turquoise'
    },
    'elements': [
        {'tag': 'markdown', 'content': '**Campaign Performance This Week**\n\n- Impressions: **120,450** (+12%)\n- Clicks: **8,320** (+8%)\n- Conversions: **342** (+15%)\n- Cost per Conversion: **\$14.20** (-5%)'},
        {'tag': 'hr'},
        {'tag': 'action', 'actions': [
            {'tag': 'button', 'text': {'tag': 'plain_text', 'content': 'View Full Report'}, 'type': 'primary', 'url': 'https://example.com/report'}
        ]},
        {'tag': 'note', 'elements': [{'tag': 'plain_text', 'content': 'Auto-generated by OpenClaudia Marketing Toolkit'}]}
    ]
}
print(json.dumps(json.dumps(card)))
")
  }"

3.4 Upload an Image

Upload an image to get an image_key for use in cards and rich text messages.

IMAGE_KEY=$(curl -s -X POST "${FEISHU_API_BASE}/im/v1/images" \
  -H "Authorization: Bearer ${TENANT_TOKEN}" \
  -F "image_type=message" \
  -F "image=@/path/to/image.png" | python3 -c "import json,sys; print(json.load(sys.stdin).get('data',{}).get('image_key',''))")

echo "Image key: ${IMAGE_KEY}"

3.5 Send to a Specific User (by email or user_id)

# By email (receive_id_type=email)
curl -s -X POST "${FEISHU_API_BASE}/im/v1/messages?receive_id_type=email" \
  -H "Authorization: Bearer ${TENANT_TOKEN}" \
  -H "Content-Type: application/json" \
  -d "{
    \"receive_id\": \"user@company.com\",
    \"msg_type\": \"text\",
    \"content\": \"{\\\"text\\\": \\\"Direct message from the marketing bot.\\\"}\"
  }"

4. Message Templates

4.1 Product Announcement

send_product_announcement() {
  local TITLE="$1"
  local VERSION="$2"
  local FEATURES="$3"
  local DOCS_URL="$4"
  local CTA_URL="$5"

  curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
    -H "Content-Type: application/json" \
    -d "$(python3 -c "
import json
card = {
    'msg_type': 'interactive',
    'card': {
        'header': {
            'title': {'tag': 'plain_text', 'content': '${TITLE}'},
            'template': 'green'
        },
        'elements': [
            {'tag': 'markdown', 'content': '**Version ${VERSION}** is now available!\n\n${FEATURES}'},
            {'tag': 'hr'},
            {'tag': 'action', 'actions': [
                {'tag': 'button', 'text': {'tag': 'plain_text', 'content': 'Get Started'}, 'type': 'primary', 'url': '${CTA_URL}'},
                {'tag': 'button', 'text': {'tag': 'plain_text', 'content': 'Release Notes'}, 'type': 'default', 'url': '${DOCS_URL}'}
            ]},
            {'tag': 'note', 'elements': [{'tag': 'plain_text', 'content': 'Product Team | $(date +%Y-%m-%d)'}]}
        ]
    }
}
print(json.dumps(card))
")"
}

4.2 Team Update / Weekly Report

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d '{
    "msg_type": "interactive",
    "card": {
      "header": {
        "title": {"tag": "plain_text", "content": "Weekly Marketing Report - W03 2025"},
        "template": "blue"
      },
      "elements": [
        {
          "tag": "column_set",
          "flex_mode": "bisect",
          "columns": [
            {
              "tag": "column",
              "width": "weighted",
              "weight": 1,
              "elements": [
                {"tag": "markdown", "content": "**Traffic**\n\nSessions: **45,230**\nUnique Visitors: **32,100**\nBounce Rate: **42%**"}
              ]
            },
            {
              "tag": "column",
              "width": "weighted",
              "weight": 1,
              "elements": [
                {"tag": "markdown", "content": "**Conversions**\n\nSignups: **580**\nTrials: **120**\nPaid: **34**"}
              ]
            }
          ]
        },
        {"tag": "hr"},
        {
          "tag": "markdown",
          "content": "**Top Performing Content:**\n1. \"10 Tips for Better SEO\" - 8,200 views\n2. \"Product Comparison Guide\" - 5,100 views\n3. \"Customer Success Story: Acme Corp\" - 3,800 views\n\n**Action Items:**\n- [ ] Publish Q1 campaign landing page\n- [ ] Review ad spend allocation\n- [ ] Schedule social media posts for next week"
        },
        {
          "tag": "action",
          "actions": [
            {
              "tag": "button",
              "text": {"tag": "plain_text", "content": "Full Dashboard"},
              "type": "primary",
              "url": "https://example.com/dashboard"
            }
          ]
        },
        {
          "tag": "note",
          "elements": [
            {"tag": "plain_text", "content": "Marketing Team | Auto-generated weekly report"}
          ]
        }
      ]
    }
  }'

4.3 Event Notification

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d '{
    "msg_type": "interactive",
    "card": {
      "header": {
        "title": {"tag": "plain_text", "content": "Upcoming Webinar: AI in Marketing"},
        "template": "purple"
      },
      "elements": [
        {
          "tag": "markdown",
          "content": "Join us for an exclusive webinar on leveraging AI for marketing success.\n\n**Date:** Thursday, January 30, 2025\n**Time:** 2:00 PM - 3:30 PM (PST)\n**Speaker:** Jane Smith, VP of Marketing\n**Format:** Live presentation + Q&A\n\n**What you will learn:**\n- How to use AI for content personalization\n- Automating campaign optimization\n- Measuring AI-driven marketing ROI"
        },
        {"tag": "hr"},
        {
          "tag": "action",
          "actions": [
            {
              "tag": "button",
              "text": {"tag": "plain_text", "content": "Register Now"},
              "type": "primary",
              "url": "https://example.com/webinar/register"
            },
            {
              "tag": "button",
              "text": {"tag": "plain_text", "content": "Add to Calendar"},
              "type": "default",
              "url": "https://example.com/webinar/calendar"
            }
          ]
        },
        {
          "tag": "note",
          "elements": [
            {"tag": "plain_text", "content": "Limited to 200 seats | Free for all team members"}
          ]
        }
      ]
    }
  }'

4.4 Marketing Campaign Alert

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d '{
    "msg_type": "interactive",
    "card": {
      "header": {
        "title": {"tag": "plain_text", "content": "Campaign Alert: Budget Threshold Reached"},
        "template": "orange"
      },
      "elements": [
        {
          "tag": "markdown",
          "content": "**Google Ads - Q1 Brand Campaign** has reached **80%** of its monthly budget.\n\n| Metric | Value |\n|--------|-------|\n| Budget | $10,000 |\n| Spent | $8,042 |\n| Remaining | $1,958 |\n| Days Left | 8 |\n| Projected Overspend | $2,100 |\n\n**Recommendation:** Reduce daily bid cap by 15% or pause low-performing ad groups."
        },
        {
          "tag": "action",
          "actions": [
            {
              "tag": "button",
              "text": {"tag": "plain_text", "content": "Adjust Budget"},
              "type": "danger",
              "url": "https://ads.google.com/campaigns"
            },
            {
              "tag": "button",
              "text": {"tag": "plain_text", "content": "View Campaign"},
              "type": "default",
              "url": "https://example.com/campaigns/q1-brand"
            }
          ]
        }
      ]
    }
  }'

5. Helper: Build and Send Cards Programmatically

For complex or dynamic cards, use Python to construct the JSON payload:

python3 -c "
import json, subprocess, os

webhook_url = os.environ.get('FEISHU_WEBHOOK_URL', '')
if not webhook_url:
    print('Error: FEISHU_WEBHOOK_URL not set')
    exit(1)

# Build card dynamically
card = {
    'msg_type': 'interactive',
    'card': {
        'header': {
            'title': {'tag': 'plain_text', 'content': 'Dynamic Card Title'},
            'template': 'blue'
        },
        'elements': []
    }
}

# Add content blocks
card['card']['elements'].append({
    'tag': 'markdown',
    'content': 'This card was built programmatically.\n\n**Key metrics:**\n- Users: 10,000\n- Revenue: \$50,000'
})

# Add a divider
card['card']['elements'].append({'tag': 'hr'})

# Add buttons
card['card']['elements'].append({
    'tag': 'action',
    'actions': [
        {
            'tag': 'button',
            'text': {'tag': 'plain_text', 'content': 'Learn More'},
            'type': 'primary',
            'url': 'https://example.com'
        }
    ]
})

# Add footer
card['card']['elements'].append({
    'tag': 'note',
    'elements': [{'tag': 'plain_text', 'content': 'Sent via OpenClaudia'}]
})

payload = json.dumps(card)
result = subprocess.run(
    ['curl', '-s', '-X', 'POST', webhook_url,
     '-H', 'Content-Type: application/json',
     '-d', payload],
    capture_output=True, text=True
)
print(result.stdout)
"

6. Bilingual Support (Chinese + English)

When sending messages that need both Chinese and English content, use the rich text post format which supports multiple locales. Feishu will display the locale matching the user's language setting.

curl -s -X POST "${FEISHU_WEBHOOK_URL}" \
  -H "Content-Type: application/json" \
  -d '{
    "msg_type": "post",
    "content": {
      "post": {
        "zh_cn": {
          "title": "重要通知：系统维护",
          "content": [
            [
              {"tag": "text", "text": "我们将于 "},
              {"tag": "text", "text": "1月25日 22:00-02:00 (北京时间)", "un_escape": true},
              {"tag": "text", "text": " 进行系统维护。"}
            ],
            [
              {"tag": "text", "text": "维护期间服务将暂时不可用。如有问题请联系 "},
              {"tag": "a", "text": "技术支持", "href": "https://example.com/support"},
              {"tag": "text", "text": "。"}
            ]
          ]
        },
        "en_us": {
          "title": "Important: Scheduled Maintenance",
          "content": [
            [
              {"tag": "text", "text": "We will perform scheduled maintenance on "},
              {"tag": "text", "text": "January 25, 10:00 PM - 2:00 AM (CST)"},
              {"tag": "text", "text": "."}
            ],
            [
              {"tag": "text", "text": "Services will be temporarily unavailable. For questions, contact "},
              {"tag": "a", "text": "Support", "href": "https://example.com/support"},
              {"tag": "text", "text": "."}
            ]
          ]
        }
      }
    }
  }'

7. Error Handling

Webhook Response Codes

Common Troubleshooting

Message not delivered:

• Verify the webhook URL is correct and the bot is still in the group
• Check that msg_type matches the content structure
• For signed webhooks, ensure the timestamp is within 1 hour of current time

Card not rendering:

• Validate JSON structure: header and elements are both required
• Button URLs must start with http:// or https://
• Markdown in cards supports a limited subset: bold, italic, links, lists, tables

API token errors:

• Tenant access tokens expire after 2 hours; re-fetch before sending
• Ensure the app has been published and approved in the developer console
• Verify im:message:send_as_bot permission is granted

Rate Limits

8. Workflow: Post Marketing Content to Feishu/Lark

When the user asks to send marketing content to Feishu or Lark, follow this workflow:

Step 1: Check Credentials

Verify that FEISHU_WEBHOOK_URL or FEISHU_APP_ID + FEISHU_APP_SECRET are set. If not, guide the user through setup.

Step 2: Determine Message Type

Step 3: Compose the Message

• Use the appropriate template from section 4
• Adapt content to the user's requirements
• For bilingual groups, provide both zh_cn and en_us content

Step 4: Preview and Confirm

Show the user the full JSON payload before sending. Explain what the message will look like.

Never auto-send without explicit user confirmation.

Step 5: Send

Execute the curl command and report the response.

Step 6: Verify

Check the response code. If code: 0, the message was delivered. If there is an error, troubleshoot using the error table above.

9. Advanced: Message Card JSON Schema Quick Reference

{
  "msg_type": "interactive",
  "card": {
    "header": {                          // Required
      "title": {
        "tag": "plain_text",
        "content": "string"
      },
      "template": "blue|green|red|..."   // Header color
    },
    "elements": [                        // Required, array of blocks
      {"tag": "markdown", "content": "..."}, // Rich content
      {"tag": "hr"},                         // Divider line
      {"tag": "img", "img_key": "...", "alt": {...}}, // Image
      {                                      // Multi-column layout
        "tag": "column_set",
        "flex_mode": "bisect|trisect|...",
        "columns": [
          {"tag": "column", "width": "weighted", "weight": 1, "elements": [...]}
        ]
      },
      {                                      // Action buttons
        "tag": "action",
        "actions": [
          {"tag": "button", "text": {...}, "type": "primary|danger|default", "url": "..."}
        ]
      },
      {                                      // Footer note
        "tag": "note",
        "elements": [{"tag": "plain_text", "content": "..."}]
      }
    ]
  }
}

Tips

• Start with webhooks. Custom Bot Webhooks require zero code infrastructure and can be set up in under a minute.
• Use interactive cards for anything beyond simple text. They are more readable and actionable.
• Include action buttons in every marketing card. Drive recipients to a landing page, dashboard, or sign-up form.
• Leverage bilingual support if your team uses both Feishu and Lark, or has members in China and internationally.
• Respect rate limits. For bulk messaging (e.g., sending to multiple groups), add a 1-second delay between requests.
• Test in a private group first before sending to large team channels.
• Keep card content concise. Cards have a maximum content size of approximately 30KB. For very long reports, link to an external page.
• Use the Feishu Message Card Builder for visual card design: https://open.feishu.cn/tool/cardbuilder (Feishu) or https://open.larksuite.com/tool/cardbuilder (Lark).