Just back from a trip to the vet for Precious yesterday, for this same issue, except a little more frequent. She was negative for parasites and I also had them check for impacted anal glands, which were also (mercifully) fine. I suspect that the mucous-like substance you're seeing is the normal excreta from these glands, a lubrication to help ease the passage of feces.
W/regard to the blood, in our case, the vet called it "frank blood," meaning it was separate from the stool, which indicated that it was most likely from irritation far down in the tract (just irritation of the rectal lining, rather than a more serious internal bleeding injury). Second, she pointed out that in the stool sample I brought in there was a significant amount of compacted hair, which can act like an abrasive torpedo passing through the intestines. Third, since the stool still looked solid and Precious' weight, coat, eyes, behavior and appetite all seemed quite healthy, she maintained that "hairball scour" was the most likely cause, and advised us to address it by brushing more often to keep the majority of hair on the *outside* of the cat, and to sneak a little vaseline onto her paws so she would lick it off. We're also trying a restricted-ingredient diet at the same time, to see if it might be an allergy.
But if the blood still appears after a couple weeks on this plan, she said she would recommend trying an anti-inflammatory injection, like cortisone. And if that doesn't work, then we let the referral clinic vet know he may be getting that new boat this year after all, in case she needs to come in for endoscopy.