This is something that checkstyle has in java and I think I might implement this rule.

Where a complete sentence one that must start with a capitol letter and end end with a period.
This can also be added with the description requires a new line and we can say that the first sentence must have a separate line from the other sentences (even if both sentences are on the same line)

Basically an example is

/**
 * This is a valid description.
 */
function foo() {
}

/**
 * this is invalid.
 */
function bar() {
}

/**
 * This is also invalid
 */
function foobar() {
}

The extra combined rule with the newline and the complete sentence are both true.

/**
 * This is the first sentence. This second sentence must be on a new line
 */
function func() {
}