Here's what to watch on ECB decision day

"Actions speak louder than words," or so the saying goes. But for global central banks fighting off global recession since 2008, it has often been the case that their words have proved just as important as actions in explaining more unconventional monetary policies, and moving markets.

We expect no action from the European Central Bank (ECB) when it meets this Thursday. However, we do think investors should pay close attention to ECB President Draghi's words at the post-decision press conference. He is likely to respond to three key questions that many in the markets, including us, would like answered. First, are current policy measures like negative interest rates doing more harm than good? Second, are more out-of-the-box policy options like "helicopter money" in discussion? Third, what is the ECB's early take on longer-term growth and inflation?

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Since the ECB's last meeting on March 10, economic, price and financial conditions at home and abroad have improved.

Lead indicators of global growth like purchasing managers' indices have firmed in the U.S. and China, and at home, retail sales data, especially in Germany, indicated still solid consumption growth. Headline consumer price inflation rose out of deflation territory, while oil's bounce off 2016 lows should pose less near-term risk to general prices. After a turbulent first quarter in the markets, global financial conditions have eased as spreads on the riskiest debt tightened, and the "fear gauge" on euro-zone stocks (the VSTOXX Index) declined towards year-to-date lows.

In short, we do not expect the ECB to add more stimulus this week, but investors will still do well to tune in to the press conference.

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The first topic we expect Draghi to speak about is negative rates. Markets want answers to the charge that sub-zero rates are doing more harm than good, squeezing bank profits rather than spurring them to lend.

We are looking for confirmation that the ECB's main policy focus is supporting credit creation via the targeted long-term refinancing operations for the banks (TLTRO II) and corporate bond buying program, details of which could be announced on Thursday.

If markets are reassured that the ECB will only lower deposit rates further in the event of a deflationary shock, Eurozone banks shares may recoup some of their near 20 percent year-to-date losses and regain some of their confidence to lend. Easier financing conditions and stronger credit demand could eventually follow, boosting euro-zone consumption, business investment, and earnings along the way.

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Second, Draghi may face questions on whether the central bank has discussed "helicopter money" in more detail, as a further policy innovation if inflation takes a nose dive. ECB Chief Economist Peter Praet recently said that the concept of the central bank printing money and distributing it directly to consumers was "not on the table." Growing discontent in Germany about the ECB's ultra-loose monetary settings makes it unlikely that Draghi will endorse direct monetary financing for now.

But hints that the central bank is undertaking further research into the concept could reassure investors that policy makers are still willing to do whatever it takes to meet the price stability target. Such pragmatism may ease some investors' fears that central banks are running out of ammo.

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A third topic Draghi may touch upon is the ECB's own forecasts for growth and inflation. Official predictions out to 2018 are only set to be released at the central bank's June meeting. However, the important Survey of Professional Forecasters is due to be published on April 22. If Draghi suggests there may be upgrades to inflation expectations out to 2020 above the 1.8 percent forecast in the first quarter, market fears about persistently low inflation in Europe may be eased, and appetite for European assets could rise as well.

Prior ECB policy actions should lead to stronger economic activity and rising inflation through 2016. Absent higher market volatility or a slump in oil, the ECB is unlikely to take any further action for now. But investors will search the ECB's words for clues about future action.

Commentary by Mark Haefele, global chief investment officer at UBS Wealth Management, overseeing the investment strategy for $2 trillion in invested assets. Follow UBS on Twitter @UBSamericas.

For the latest commentary on the markets in the U.S. and around the world, follow @cnbcopinion on Twitter.