deploy: 9e1a09eec0

features/binary_formats/cbor.md

@@ -174,7 +174,20 @@ The library maps CBOR types to JSON value types as follows:
 
 !!! warning "Object keys"
 
-    CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps with keys other than UTF-8 strings are rejected.
+    CBOR allows map keys of any type, whereas JSON only allows strings as keys in object values. Therefore, CBOR maps
+    with keys other than text strings (major type 3) are rejected with a
+    [`parse_error.113`](../../home/exceptions.md#jsonexceptionparse_error113) exception (or, with `allow_exceptions` set
+    to `false`, a discarded value) naming the type of the key that was found, for instance:
+
+    ```
+    [json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR object key: only string keys are supported, but found an unsigned integer; last byte: 0x01
+    ```
+
+    This applies to the [SAX interface](../parsing/sax_interface.md) as well, as the key is read before it is passed
+    on. This is a deliberate restriction of the library's JSON value model, not an oversight: formats built on CBOR
+    maps with integer keys, such as COSE ([RFC 9052](https://www.rfc-editor.org/rfc/rfc9052.html)) or CWT
+    ([RFC 8392](https://www.rfc-editor.org/rfc/rfc8392.html)), cannot be read with this library and need a
+    general-purpose CBOR library instead.
 
 !!! warning "UTF-8 validation of text strings"