Fix: Zapier MCP “Can’t Reconnect / CEL Parse Error” in Agent Builder

Oct '25 • General

I should caveat this by saying I hope this is just a simple bug that OpenAI is currently working on and has a solution quite soon, but in the meantime, this was my experience with trying to get my MCP to connect to Zapier:

After wrestling with this for a few days, I finally figured out why my Zapier MCP kept failing to reconnect and throwing random CEL parse or 401 auth errors — even after deleting and rebuilding everything from scratch.

Now Im not 100% certain as to why the API key doesnt always seem to work, but if you continually get CEL Parse Error or 401 Auth Errors, what worked for me was to set your credentials as a header in the MCP configuration and apply the following:

Key: Authorization

Value: Bearer <your_api_key>

Once I saved that and re-tested the connection, it passed instantly. No more CEL errors, no 401s — clean handshake and data started flowing again.

If you’re seeing the same problem (connection test failing after a token refresh), try switching to header-based auth. It looks like Agent Builder currently parses the Access Token field incorrectly in some cases, especially after key rotation.

Next is to figure out how to keep this connection going cause from my understanding the Auth Tokens need to be rotated every 24-48 hours which is turbo annoying.

Anyways, hope that helps someone.

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