diff --git a/dspy/signatures/signature.py b/dspy/signatures/signature.py
index 236a774ddd..f33df96ef0 100644
--- a/dspy/signatures/signature.py
+++ b/dspy/signatures/signature.py
@@ -245,6 +245,31 @@ class Signature(BaseModel, metaclass=SignatureMeta):
 
     @classmethod
     def with_instructions(cls, instructions: str) -> type["Signature"]:
+        """Return a new Signature class with identical fields and new instructions.
+
+        This method does not mutate `cls`. It constructs a fresh Signature
+        class using the current fields and the provided ``instructions``.
+
+        Args:
+            instructions (str): Instruction text to attach to the new signature.
+
+        Returns:
+            type[Signature]: A new Signature class whose fields match `cls.fields`
+            and whose instructions equal ``instructions``.
+
+        Example:
+            ```
+            from dspy.signatures import Signature, InputField, OutputField
+
+            class MySig(Signature):
+                input_text: str = InputField(desc="Input text")
+                output_text: str = OutputField(desc="Output text")
+
+            NewSig = MySig.with_instructions("Translate to French.")
+            assert NewSig is not MySig
+            assert NewSig.instructions == "Translate to French."
+            ```
+        """
         return Signature(cls.fields, instructions)
 
     @classmethod