Texas licenses plumbers through the Texas State Board of Plumbing Examiners, a separate agency from TDLR. TSBPE publishes no bulk extract and no open API, so Texas plumbers cannot be verified through this API — the TSBPE website is the only source, and it has to be checked by hand.
Try a free lookup — no signup, right here on this page. For programmatic access, take a free API key — 250 requests a month, no card. Also on RapidAPI and, if you would rather not write code at all, the Apify Store.
Full coverage detail, including the caveats that apply to every Texas lookup, is on the Texas page.
The API is on RapidAPI with a free tier: Contractor License Verification. It is also on the Apify Store: Contractor License Lookup & Verification. Full schema at /docs.