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

Click "New Agent" at

In the prompt field ("How can I help you?"), type:

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

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

Step 2: Configure the Webhook Trigger

Click the trigger node at the top of the workflow canvas
Select Webhook Received

Copy the generated URL:

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

Click Generate Secret — copy immediately (shown once)

Step 3: Add the Slack Action

Click "+" to add a step
Search for Slack Send Channel Message
Authorize your Slack workspace when prompted

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

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.

Output

The finished agent accepts the test webhook, creates one completed Lindy task, and posts one concise Slack summary without exposing the webhook secret. Keep the agent URL, task ID, and sanitized test payload as the setup receipt so the workflow can be retested after changes.

Examples

Send an order.created event to a test-only webhook and confirm that the configured Slack channel receives “Jane Doe placed a $149.99 order for Widget Pro and Adapter Cable.” If the request returns 401, replace the placeholder secret with the webhook secret generated for that same agent rather than a different workspace credential.

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

Next Steps

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

lindy-hello-world