Hunter.io is a popular tool for finding and verifying professional email addresses. Connecting it to OpenClaw means your sales team can look up email addresses, search by company domain, and verify contact info directly from Slack without switching tools.
How OpenClaw Integrations Work
OpenClaw is a self-hosted AI assistant that runs on your own server — typically an EC2 instance — and connects to Slack. It uses Claude under the hood to process requests. Out of the box, OpenClaw doesn't ship with pre-built connections to third-party tools. Instead, integrations are built using the skills system: markdown files in ~/.openclaw/skills/ that give Claude instructions for a particular domain, combined with HTTP tool calls to any API you expose to it.
In practice, adding a real integration means: getting API credentials from the third-party service, building or configuring a small proxy/endpoint that OpenClaw can call, and writing a skill file that tells Claude how to use it. For some tools this is an afternoon of work. For others — like Hunter.io — it's considerably more involved.
Connecting OpenClaw with Hunter.io: Step by Step
Step 1: Get Your Hunter API Key
Log into Hunter.io and go to API in the top navigation. Copy your API key. The Hunter API base URL is https://api.hunter.io/v2/. All requests use this key as the api_key query parameter.
Step 2: Use the Domain Search and Email Finder Endpoints
Key endpoints: /domain-search?domain=&api_key= (find email addresses associated with a domain), /email-finder?domain=&first_name=&last_name= (find a specific person's email), /email-verifier?email= (verify deliverability of an email address). These cover the most common sales team use cases.
Step 3: Build the Proxy and Skill File
Wrap the domain search, email finder, and verifier endpoints. Write ~/.openclaw/skills/hunter.md documenting what lookups are available. Include guidance for Claude on what to do with the confidence scores Hunter returns — a score below 70 typically means the address is uncertain.
Challenges and Caveats
Monthly Request Limits
Hunter's API usage is counted against your monthly plan limit. High-volume use (e.g., bulk domain searches triggered by OpenClaw) can exhaust your plan faster than expected. Cache results and avoid redundant lookups.
Accuracy Isn't Guaranteed
Hunter finds email patterns based on publicly indexed information. Confidence scores indicate reliability, but lower-confidence results will have higher bounce rates. Factor this into how Claude presents results — high-confidence results warrant different actions than low-confidence ones.
Skip All of This — Use Cody Instead
Cody has Hunter.io integration built in. Find and verify email addresses from Slack without API key setup.
Related Guides
- Connecting OpenClaw with Apollo: A Practical Guide
- Connecting OpenClaw with Clay: A Practical Guide
- Connecting OpenClaw with Instantly: A Practical Guide
Need the model-flexible version? See: How to Connect Hunter.io to OpenClaw: Setup, Models, and Workflow Guide.