Clay's webhook receiver has quirks with certain content types, and application/vnd.api+json is one of them. The parser expects standard application/json and doesn't handle JSON API spec formatting well.
Quick workaround: Set up a simple middleware layer using Zapier or n8n to receive the webhook from Outreach, then forward it to Clay with proper application/json headers. Takes 5 minutes to build and costs basically nothing.
If you're technical, you can also use a lightweight Node.js function on Vercel or Railway. Just strip the JSON API wrapper and forward the actual data payload to Clay's webhook URL.
Alternative approach: Instead of webhooks, consider pulling data from Outreach via their API directly in Clay using the HTTP API enrichment. You lose real-time updates but gain more control over the data format. Set up a scheduled run every 15-30 minutes depending on your volume.
I've seen teams also use Outreach's Salesforce sync as an intermediary - sync to SFDC first, then webhook from there to Clay. More steps but rock solid reliability.
The JSON API content type limitation isn't documented anywhere obvious, but it's a known issue. Clay's engineering team is aware but no timeline on native support. The middleware approach is your cleanest bet for now.