Smart Contract Event Monitor (Web3)
Smart Contract Event Monitor (Web3) This workflow automatically monitors the Ethereum blockchain, extracts USDT transfer events, filters large-value transactions, stores them in Airtable and sends a clean daily summary alert to Slack. This workflow checks the latest Ethereum block every day and identifies high-value USDT transfers. It fetches on-chain logs using Alchemy, extracts sender/receiver/value details, filters transactions above a threshold, stores them in Airtable and finally sends a single clear summary alert to Slack. You receive: Daily blockchain check (automated) Airtable tracking of all high-value USDT transfers A Slack alert summarizing the count + the largest transfer Ideal for teams wanting simple, automated visibility of suspicious or large crypto movements without manually scanning the blockchain. Quick Start – Implementation Steps Add your Alchemy Ethereum Mainnet API URL in both HTTP nodes. Connect and configure your Airtable base & table. Connect your Slack credentials and set the channel for alerts. Adjust the value threshold in the IF node (default: 1,000,000,000). Activate the workflow — daily monitoring begins instantly. What It Does This workflow automates detection of high-value USDT transfers on Ethereum: Fetches the latest block number using Alchemy. Retrieves all USDT Transfer logs from that block. Extracts structured data: Sender Receiver Amount Contract Block number Transaction hash Filters only transactions above a configurable threshold. Saves each high-value transaction into Airtable for record-keeping. Generates a summary including: Total number of high-value transfers The single largest transfer Sends one clean alert message to Slack. This ensures visibility of suspicious or large fund movements with no repeated alerts. Who’s It For This workflow is ideal for: Crypto analytics teams Blockchain monitoring platforms Compliance teams tracking high-value activity Web3 product teams Developers needing automated USDT transfer tracking Anyone monitoring whale movements / suspicious transactions Requirements to Use This Workflow To run this workflow, you need: n8n instance** (cloud or self-hosted) Alchemy API URL** (Ethereum Mainnet) Airtable base** + Personal Access Token Slack workspace** with API permissions Basic understanding of Ethereum logs, hex values & JSON data How It Works Daily Check – Workflow runs automatically at your set time. Get Latest Block Number – Fetches newest Ethereum block from Alchemy. Fetch USDT Logs – Queries all Transfer events (ERC-20 standard). Extract Transaction Details – Converts hex → readable data. Filter High-Value Transactions – Keeps only large value transfers. Save to Airtable – Adds each transfer record to your database. Generate Summary – Finds the largest transfer & total count. Send Slack Alert – Notifies your team with one clean summary. Setup Steps Import the provided n8n JSON file. Open the Get Latest Block and Fetch Logs HTTP nodes → add your Alchemy API URL. Ensure USDT contract address (already included):0xdAC17F958D2ee523a2206206994597C13D831ec7 Connect your Airtable account and map: Contract From Address To Address Value Block Number txHash Connect Slack API credentials and choose your channel. Change the threshold limit in the IF node if needed (default: 1B). Activate the workflow — done! How To Customize Nodes Customize Value Threshold Modify the IF node: Increase or decrease the minimum transfer value Change logic to smaller or larger whale-tracking Customize Airtable Storage You can add fields like: Timestamp Token symbol USD price (using price API) Transaction status Risk classification Customize Slack Alerts You may add: Emojis Mentions (@channel, @team) Links to Etherscan Highlighted blocks for critical transfers Customize Web3 Provider Replace Alchemy with: Infura QuickNode Public RPC (not recommended for reliability) Add-Ons (Optional Enhancements) You can extend this workflow to: Track multiple ERC-20 tokens Process several blocks instead of just the latest Add price conversion (USDT → USD value) Detect transfers to suspicious wallets Generate daily or weekly summary reports in Slack Create a dashboard using Airtable Interfaces Add OpenAI-based insights (large spike, suspicious pattern, etc.) Use Case Examples 1\. Whale Tracking Detect large USDT movements (>1M or >5M). 2\. Compliance Monitoring Log high-value transfers in Airtable for audits. 3\. Real-Time Alerts Slack alerts tell your team instantly about big movements. 4\. On-Chain Analytics Automate structured extraction of Ethereum logs. 5\. Exchange Monitoring Detect large inflows/outflows to known addresses. Troubleshooting Guide | Issue | Possible Cause | Solution | |------------------------|-----------------------------------|---------------------------------------------------------| | No data in Airtable | Logs returned empty | Ensure USDT transfer events exist in that block | | Values are “zero” | Hex parsing failed | Check extract-code logic | | Slack alert not sent | Invalid credentials | Update Slack API key | | Airtable error | Wrong field names | Match Airtable column names exactly | | HTTP request fails | Wrong RPC URL | Re-check Alchemy API key | | Workflow not running | Schedule disabled | Enable "Daily Check" node | Need Help? If you need help customizing or extending this workflow — adding multi-token monitoring, setting up dashboards, improving alerts or scaling this for production — our n8n workflow developers at WeblineIndia can assist you with advanced automation. An n8n automation workflow template by WeblineIndia.
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