diff --git a/AGENTS.md b/AGENTS.md
index 5e455ec91521..e5952f85c45b 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -37,6 +37,11 @@ simulation case, use the project-level skill in
     supercomputer via a gitlab pipeline. The tests are written using
     [reframe](https://reframe-hpc.readthedocs.io/en/stable/). These are
     validation tests checking that important cases produce the expected output.
+  - *Important*: Since Neko can be run in both double and single precision,
+    numerical assertions in tests should adjust their tolerance based on the
+    kind of `rp`. The `math` module contains the `NEKO_EPS` parameter that is
+    set to the correct machine epsilon for `rp`, thus in Fortran code tolerances
+    can be conveniently defined via its value.
 
 ### Unit tests with pFUnit.
 - A guideline for writing these tests is given in