I have resolved this question now so I am posting the details here in case anybody else has the same problem and refers to this.
1. Calling the Support Number is easier said than done. It starts with the usual automated nonsense where it insists on texting or emailing me some information, which in turn is only telling me how to contact Support. There is no obvious option to speak with a human After calling back again, I figured out that saying "Speak to a person" or something like that allowed me to get past the automated system into a human.
2. The first human was less than helpful, claimed he was having system problems, and promised to call me back. I suspected this was malarkey but I waited a couple of hours to give him a chance to do his job. After giving up, I called again and luckily got a different human.
3. This person (Mirza) was actually professional and helped me understand the problem. It turns out that Tradesperson's Tools are only deductible once they exceed a certain value ($1368 as of this year). To confirm, I entered fake amounts greater than $1368 and could see the calculation was working fine. Since I "only" spent around $500 on tools for work this year, it looks like no tax break for me.
Here is a CRA link that explains the gory detail:
Deduction for tools (tradespersons) - Canada.ca
