"Backend error: 'INVALID_INPUT'" for RKD API retrieve news headlines

Good day,

I was calling the RKD API to retrieve the news headlines with specific topics. Looks like if I place too many topics there, it will be prompted with "Backend error: 'INVALID_INPUT'":

{

"Fault": {

"Code": {

"Value": "s:Receiver",

"Subcode": {

"Value": "a:General_Errors"

}

},

"Reason": {

"Text": {

"lang": "en-US",

"Value": "Backend error: 'INVALID_INPUT'"

}

},

"Detail": {

"ClientErrorReference": {

"Timestamp": "2021-04-25T07:02:26.1319766Z",

"ErrorReference": "e046c5a25df44e848848ed9c1e3443e7",

"ServerReference": "9EB52DEFB1853C9230A344FBDFD9B815D5EBF21709E0E901"

}

}

}

}

Do we have guideline or documentation on this limitation, i.e., the maximum length of the request body?

One more fact, if I remove the "lanaguage" filter condition, then I may even place 2 or more topics condition there, so I guess there's some limitations on the length of the string in the request body.

Attach the sample request:

(if just remove one topic condition, e.g., the last "AAA", then it will pass)

Sample Request.txt