How to pass headers to a fastmcp client?

[rrondir]

Right now this is what I'm doing:
async with Client(StreamableHttpTransport(url=url, headers=headers)) as client:

But when running the client.list_tools() I get an error saying client is not connected, doing just async with Client(url) as client: works

Any idea how to make it work?

[jlowin]

That is the correct setup; is it an SSE server (not streamable HTTP) or an invalid header? If you can replicate with an MRE, please open an issue

[rrondir]

The issue was on the server, I had a wrong implementation and the error message was confusingly propagating to the client throwing me off