Singular vs. plural for a noun that is associated to a plural number of another noun

You should use 'Alternative 1' if you need a description for each report, which is what you wanted. Only use the other one if you need a description for the five reports, as a whole. I shall explain. In 'Alternative 1', you said you needed 'one-liner descriptions for all five reports'. This means that you need more than one description for the five reports. In 'Alternative 2', you said you needed 'one-liner description for all five reports'. This means that you only need one description for the five reports. I was just checking back on this post and saw Edwin Ashworth's comment: "I need a one-line description for each of the five reports we are going to present tomorrow." I suggest you use his suggestion as it is more clear and direct.