Function probe 

pub async fn probe(transport: &str, config_json: &str) -> ProbeResult

Probe a server given its transport ("stdio" | "http" | "sse" | any other free-text value from the pre-v11 field, treated as stdio for back-compat) and its raw config JSON blob — the exact object agent_config::build_mcp_config_from_refs merges into .mcp.json.