FLT CREW EXPERIENCED CONFLICT AT FL230 WHEN ATC DESCENDED TFC THROUGH OCCUPIED ALT; ALERTED BY TCAS; PREVENTED A LOSS OF SEPARATION.

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I BELIEVE ATC EITHER FORGOT ABOUT OUR POS (OR THE DSNDING ACFT'S POS) OR DIDN'T EXERCISE PROPER JUDGEMENT BY NOTIFYING US. I'M NOT GOING TO WAIT FOR A BOX OR MACHINE (TCAS) TO TELL ME WHAT TO DO. EVASIVE ACTION WAS APPROPRIATE AND NECESSARY. CRUISING AT FL230 ON THE TRAKE 8 N OF SGF; WE NOTICED AN ACFT DSNDING ABOVE US (FROM SEVERAL THOUSAND FT ABOVE) AND A FEW HUNDRED FT HORIZONTALLY IN FRONT OF OUR POS. ATC NEVER CALLED OUT THE SAID TFC. TFC CONTINUED TO DSND THROUGH 2000 FT ABOVE. WE ASKED ATC (ZKC 128.6) ABOUT THE TFC -- HE DID NOT RESPOND. AT 1200 FT ABOVE OUR ALT; WE ASKED ATC AGAIN -- STILL NO RESPONSE. WHEN IT BECAME APPARENT TFC WAS DSNDING THROUGH 1000 FT ABOVE US; I TURNED OFF COURSE ABOUT 30 DEGS TO THE L TO AVOID TFC. WE SIMULTANEOUSLY NOTIFIED ATC OF OUR DEV; BUT ALL HE DID WAS HAND US OFF TO THE NEXT SECTOR. OUR TCAS SHOWED TFC LEVELING OFF 700 FT ABOVE. WE NOTIFIED NEXT CTLR OF DEV. TCAS MAY OR MAY NOT HAVE GIVEN A TA -- I WAS TAKING EVASIVE ACTION SO MY/OUR ATTN WAS DIVERTED SOLELY TO THE OUTSIDE OF OUR ACFT. COMMON SENSE DICTATED A DEV. I TURNED 30 DEGS TO THE L OF ARR COURSE AND NOTIFIED ATC. THIS IS AN ATC ISSUE. THE CTLR SHOULD HAVE CALLED OUT THE DSNDING ACFT'S POS -- ESPECIALLY DUE TO THE VERY CLOSE PROX OF THE 2 PLANES INVOLVED.