mcp-sse-client-validatio-sse-client-connects-to-an-mcp-server-that-responds-fef4ca02

THEN Modify the SSE client to validate the Content-Type header during connection initialization. If the header does not contain 'text/event-stream', raise an exception (e.g., ValueError) so that the caller can detect and handle misconfiguration. This prevents silent failures and allows early error detection.

async with sse_client(url) as (reader, writer):
    # After receiving response headers, check Content-Type
    if 'text/event-stream' not in response.headers.get('Content-Type', ''):
        raise ValueError(f"Expected Content-Type text/event-stream, got {response.headers['Content-Type']}")