Lindy Hello World

Overview

Build a minimal Lindy AI agent: Webhook Received trigger -> LLM processing -> Slack notification. Demonstrates the three core building blocks every Lindy agent uses: Trigger, Agent Step (prompt + model + skills), and Action.

Prerequisites

• Lindy account at
• Slack workspace connected (or Gmail for email variant)
• Completed lindy-install-auth setup

Instructions

Step 1: Create Agent via Dashboard

1. Click "New Agent" at
2. In the prompt field ("How can I help you?"), type:

When I send a webhook, summarize the message and post it to Slack

1. Agent Builder auto-generates the workflow with trigger + action nodes

Step 2: Configure the Webhook Trigger

1. Click the trigger node at the top of the workflow canvas
2. Select Webhook Received
3. Copy the generated URL:

https://public.lindy.ai/api/v1/webhooks/<unique-id>

1. Click Generate Secret — copy immediately (shown once)

Step 3: Add the Slack Action

1. Click "+" to add a step
2. Search for Slack Send Channel Message
3. Authorize your Slack workspace when prompted
4. Configure fields:

• Channel: #general (or test channel)
• Message field mode: AI Prompt
• Instruction:

Summarize the webhook payload in one sentence. Payload: {{webhook_received.request.body}}

Step 4: Set the Agent Prompt

Open Settings > Prompt:

You are a webhook summarizer. When you receive a webhook payload,
extract the key information and create a concise one-sentence summary.
Be factual and specific. Do not add opinions or speculation.

Step 5: Test It

bash
curl -X POST "https://public.lindy.ai/api/v1/webhooks/YOUR_ID" \
  -H "Authorization: Bearer YOUR_SECRET" \
  -H "Content-Type: application/json" \
  -d '{
    "event": "order.created",
    "customer": "Jane Doe",
    "amount": 149.99,
    "items": ["Widget Pro", "Adapter Cable"]
  }'

Expected Slack message: > Jane Doe placed a $149.99 order for Widget Pro and Adapter Cable.

Step 6: Verify in Dashboard

Navigate to the Tasks tab in your agent view. Confirm status shows Completed. Click into the task to see each step's input/output for debugging.

Agent Anatomy

| Component | Purpose | Hello World Value | |-----------|---------|-------------------| | Prompt | Core behavioral instructions | "Summarize webhook payloads" | | Model | AI engine powering decisions | Default (GPT-4 / Claude / Gemini) | | Skills | Available actions & tools | Slack Send Channel Message | | Exit Conditions | When the task is "done" | Message sent successfully |

Webhook Data Variables

| Variable | Contents | |----------|----------| | {{webhook_received.request.body}} | Full JSON payload | | {{webhook_received.request.headers}} | HTTP request headers | | {{webhook_received.request.query}} | URL query parameters |

Field Configuration Modes

| Mode | Behavior | Credit Cost | |------|----------|-------------| | Auto | Agent determines value from context | Standard | | AI Prompt | Natural language instructions generate content | Standard | | Set Manually | Exact value, no AI processing | Lower |

Variant: Email Instead of Slack

Replace the Slack action with Gmail Send Email:

• To: Set manually or reference a webhook field
• Subject: AI Prompt — "Summary: {{webhook_received.request.body.event}}"
• Body: AI Prompt — "Summarize this event: {{webhook_received.request.body}}"

Error Handling

| Issue | Cause | Solution | |-------|-------|----------| | Webhook returns 401 | Missing Authorization header | Add Bearer <secret> header | | Slack message not sent | Channel not authorized | Re-authorize Slack in Lindy | | Task shows "Failed" | Action misconfigured | Check field references in step config | | No task created | Agent not active | Publish/activate the agent | | Empty summary | Payload not reaching LLM | Verify {{webhook_received.request.body}} reference |

Cost

~1-3 credits per invocation on basic models. Free tier (400 credits/month) supports ~130-400 test runs per month.

Resources

• Getting Started 101
• Webhook Triggers Academy
• Lindy Documentation

Next Steps

Proceed to lindy-core-workflow-a for a full multi-step agent workflow.