> MMT alone may not provide sufficient guidance on how to adjust outlays and receipts to manage employment and inflation.

The primary policy prescription of MMT is the job guarantee, which explicitly addresses the question of how to manage employment and inflation. The job guarantee defines the value of the currency, with other spend floating relative to that, whilst simultaneously providing full employment. In any case, the current model is pretty broken in which fiddling with interest rates is assumed to have a direct casual link to both (and depressingly in opposite directions).

> MMT may not be politically feasible. Politicians may not be navigate politically unpopular but economical necessary.

Insomuch as descriptive MMT is what happens in most sovereign currency areas, this is just a problem of communication. You are right that getting the politics correct is both hard and important. I'm not sure the policies will in aggregate be very unpopular though once a non-made-up description of what limits spending is understood better by the population.

> MMT may be domestically sound, but challenging to implement regarding international trade. It may result in devaluing compared to other currencies.

A floating exchange rate is a feature not a bug. Current attempts to maintain a soft peg are deeply damaging domestically for many countries. In any case, countries that are confident in their monetary and fiscal policies and that have a sound economy seem to be more robust than those that try to maintain a soft peg (see Japan).

> MMT may suggest that interest rates can be kept low indefinitely. It's unclear if this would result in excessive risk taking.

Excessive risk taking needs dealing with at the political level with actual laws and regulations. Interest rate policy is a crap tool to deal with such problems.

> MMT may not be applicable to developing economies.

Why not? It explains what their actual constraints are and the risks of taking on foreign debt or pursuing an export led growth strategy etc.

> MMT may work in the short term to manage employment and demand but fail to cultivate long term economic development.

I'm not sure what this has to do with MMT. The post war period with much higher employment and stronger government intervention had much higher growth than the following monetarist/neoliberal era, so perhaps the status quo is the problematic position.

> MMT's implication as having a larger governmental impact on investment may crowd out private sector investment.

Far from crowding out, it crowds in in practice:

https://billmitchell.org/blog/?p=12022

Again, the historical evidence shows when governments stop spending, private investment collapses.

> MMT if implemented could be constrained by international investors. If international investors dislike a policy, it may have domestic implications.

What domestic implications? If you're thinking about direct foreign investment, this is problematic in its own right. It might increase domestic employment and potentially increase local skills, but it is also extractive and drains the nations' equity. This possibly has stronger implications for low income nations that don't have a good education base and well developed industries, but MMT at least makes clear where the trade-offs lie.

> MMT depends on having a government effective enough to implement it. If a government is too dysfunctional, MMT may fail in practice.

True, but then so do all political systems. MMT "failing" is also a strange concept given MMT describes the system since the fall of Bretton Woods. What's remarkable is how stable (notwithstanding the obvious "shocks") the system has been despite most governments operating as though they were still inside the Bretton Woods system.