You can make it out from the screenshot, this is a bug.
Hi. Can you provide some more information about this? E.g. Which environment did you use and which endpoint did you call?
If you are using testnet, MCO is not provided.
@ishuen Hi, this is mainnet. API /sapi/v1/asset/dust. The only bug is that the error description has changed, the language line can’t be loaded on Binance’s side in this case.
Failure to dust that asset, that is normal, it has been happening from the beginning that way 
I have less than 0.05 of that asset.
It would be helpful to include more detailed errors for dusting, as now when you dust for example BTC, ETC, DASH, MCO and only MCO is failing it still returns ‘asset not supported’ and the whole operation fails. It doesn’t tell you which asset is causing the problem.
That’s why we have to call dust per asset, which also blocks the whole dusting operation if it succeeds for another 6 hours. So if the user has more assets to dust, it can take days to fully dust. But that is another topic on itself
The error was due to this asset, MCO, and the error message is valid. Since none of the trading pair is active in the market, the system does not know its conversion rate. But yes, it would be better if which asset causes the error is specified. Will share this improvement point with the team.
To see if you can convert all assets at a time, you can first check exchangeInfo (GET /api/v3/exchangeInfo) endpoint. If all the trading pairs of a specific asset are in BREAK status, the dust transfer does not work because its rate is not available. Hence, if such an asset exists, you have to specify all the other allowed assets in the request parameter. https://binance-docs.github.io/apidocs/spot/en/#dust-transfer-user_data
@ishuen Hi, thank you for sharing the details with me Better error description would be good. But also the current bug is the description is com.binance.assetservice.AssetErrorCode.ASSET_NOT_SUPPORT which is obviously an internal langualge line lookup key. It sould be This asset is not supported. or similar. See the screenshot, originally it was like that, but then it changed.
So that is a bug / typo on Binance’s side. Better error info - that is an improvement.
Thank you!