The server dispatched requests and notifications without ever checking jsonrpc, so a missing or wrong version could invoke tools or flip notification state; Remote accepted any reply with ok/result/error without comparing ids, so a faulty endpoint could attribute a stray result to the current call. handle() now requires jsonrpc 2.0 before dispatch (other envelopes get -32600, or are ignored for notifications, which have no id for a reply) and Remote::call rejects a reply whose id doesn't echo the request's, dropping the connection so the next call starts fresh, with the usual uncertainty error. Three new tests cover wrong/missing versions (incl. batch entries and a state-changing notification) and the mismatch-reconnect; docs/mcp.md documents both. cargo test -p vectorcraft-mcp passes.