Search For Text in Dynamics 365 Task Description

[GurBAL]

I am trying to write a flow that will return D365 tasks whose Description field contains a specific text string.  In the Flow, the text string is contained in a variable called Hash (if it matters, Hash is about 95-125 characters long and has no spaces).  I am using the "List Records" action, and have tried a few different formulas in the "Filter Query" section but can't seem to make it work.  I have tried:

• substringof(description,'@{variables('Hash')}') - Results in an error during test: BadRequest "An unknown function with name 'substringof' was found"
• substringof('@{variables('Hash')}',description) - Results in an error during test: BadRequest "An unknown function with name 'substringof' was found"
• contains(description,'@{variables('Hash')}') - Flow runs successfully, but no task is returned even though there is a task whose description contains Hash.

Can anyone suggest a filter query that will return D365 Tasks that have the Hash string somewhere in the Description field?  Thanks!

[GurBAL]

One more detail.  I am evaluating whether any matching tasks are found with the following Condition: 

length(body('List_records')?['value']) is greater than 0

[GurBAL · Accepted solution]

Problem solved!  When I recreated the filter query using one of the same formulas as above (the "contains" version), but using the Dynamic Content box to build the query instead of doing it manually, the flow finished successfully and the Task was found.  Not sure why that made the difference, but thought I would update here in case someone runs into this in the future.  Cheers!