Endotoxin is a cell-wall fragment that can remain even after bacteria are no longer viable, so sterility testing alone does not confirm whether endotoxin is present. If endotoxin testing is performed, it is run as a separate assay from bioburden and sterility results and reported as a quantitative value against a defined limit rather than a pass or fail on visible growth.
The applicable limit and the units it is reported in, where endotoxin testing applies, are part of what a lot's documentation should specify. Ask which tests apply to the product and request the methods, units and results; do not assume endotoxin testing is performed for every product in a supplier's catalog.
A buyer evaluating a supplier can ask whether endotoxin testing is performed by an independent third-party laboratory, how the result is reported, and whether the number for a specific lot is available as part of that lot's certificate of analysis. Treat a statement like "we test for endotoxin" as incomplete; the actual number, the method, and the testing lab are what make the claim checkable.
Where endotoxin testing applies to a product, asking for the number rather than confirmation that testing occurred is part of basic vendor due diligence.