Safest is still human-reviewed output, not fully auto-insertion. For scale: crawl your sitemap with Screaming Frog, export it, then run a Python keyword-to-URL matching script to generate a link suggestion CSV — 30 lines of code and you have unlimited sites covered. QA the list yourself, then bulk update via SQL or a WP plugin. Fully automated tools that insert without review are where anchor over-optimization creeps in and causes actual ranking damage.