@Major Robertson Is right all those sites are MLS aggregators and contain a lot of missing or inaccurate information, to help counteract that you might also want to use the public search portal of a local brokerage, because those are usually linked to the local MLS.
My local MLS app is not that user friendly, and I have clients that use Realtor.com or other apps to browse the market and are often looking at deals that are too good to be true because they have incorrect information. I have my own personal website which uses the internet access protocol from my local MLS (it's called IDX, and that is how the aggregators pull their data also) but is hosted by a third party, so the features are not anywhere near as robust as the large aggregators offerings.
I believe Zillow is involved in some litigation with the State of Texas currently regarding their "Zestimate." Since Texas is a non-disclosure state, Zillow's pricing information is not always based on actual sale prices. Using county appraisal districts and other sources does not provide an accurate price in many areas. If you get deep into the settings on Zillow there is a way to see the "pricing accuracy" for certain areas, I believe San Antonio is rated 1 or 2 stars out of 5 stars, but that may have changed since I last checked.