The error a query returns, as {:error, %SpaceTAP.Error{}}.

:type says what went wrong:

• :service_error - the TAP service reported that the query failed, for example because of invalid ADQL or an unknown table, in a VOTable error document whose query status is ERROR (DALI 1.1 §4.4), or in plain text with HTTP 400 (DALI 1.1 §4.2). :message is its message, or says that it had none, since the message is optional (DALI 1.1 §4.4.2). A VOTable error document can come with HTTP 200 as well as 4xx or 5xx (TAP 1.1 §3.3).
• :http_error - an HTTP error status without an error document from the TAP service, such as an HTML page from a proxy. Plain text with any status other than 400 is an HTTP error too, because a proxy or web server in front of the service may have written it, and :message is that text.
• :transport_error - no response arrived: the connection failed or timed out, or the redirects never ended. :status is nil.
• :decode_error - a successful response that can't be read as a result, such as malformed CSV or a format other than the one requested.

Later versions may add types, so when you match on :type, keep a clause for the rest.

:status is the HTTP status of the response, and the message starts with it:

iex> error = %SpaceTAP.Error{type: :service_error, message: "Unknown table", status: 400}
iex> Exception.message(error)
"(HTTP 400) Unknown table"