diff --git a/langfuse/api/experiments/client.py b/langfuse/api/experiments/client.py
index a3d469217..66a90d95b 100644
--- a/langfuse/api/experiments/client.py
+++ b/langfuse/api/experiments/client.py
@@ -47,7 +47,10 @@ def list(
         Parameters
         ----------
         from_start_time : dt.datetime
-            Retrieve only experiments on or after this datetime.
+            Required. Retrieve only experiments with events on or after this
+            datetime. A lower bound is required so the query stays fast on
+            large projects; pair it with an upper bound to select a specific
+            window.
 
         fields : typing.Optional[str]
             Comma-separated list of field groups to include. Available groups:
@@ -145,7 +148,10 @@ def list_items(
         Parameters
         ----------
         from_start_time : dt.datetime
-            Retrieve only experiment items started on or after this datetime.
+            Required. Retrieve only experiment items started on or after this
+            datetime. A lower bound is required so the query stays fast on
+            large projects; pair it with an upper bound to select a specific
+            window.
 
         fields : typing.Optional[str]
             Comma-separated list of field groups to include. Available groups:
@@ -263,7 +269,10 @@ async def list(
         Parameters
         ----------
         from_start_time : dt.datetime
-            Retrieve only experiments on or after this datetime.
+            Required. Retrieve only experiments with events on or after this
+            datetime. A lower bound is required so the query stays fast on
+            large projects; pair it with an upper bound to select a specific
+            window.
 
         fields : typing.Optional[str]
             Comma-separated list of field groups to include. Available groups:
@@ -368,7 +377,10 @@ async def list_items(
         Parameters
         ----------
         from_start_time : dt.datetime
-            Retrieve only experiment items started on or after this datetime.
+            Required. Retrieve only experiment items started on or after this
+            datetime. A lower bound is required so the query stays fast on
+            large projects; pair it with an upper bound to select a specific
+            window.
 
         fields : typing.Optional[str]
             Comma-separated list of field groups to include. Available groups:
diff --git a/langfuse/api/experiments/raw_client.py b/langfuse/api/experiments/raw_client.py
index 8736786df..189c826ba 100644
--- a/langfuse/api/experiments/raw_client.py
+++ b/langfuse/api/experiments/raw_client.py
@@ -45,7 +45,10 @@ def list(
         Parameters
         ----------
         from_start_time : dt.datetime
-            Retrieve only experiments on or after this datetime.
+            Required. Retrieve only experiments with events on or after this
+            datetime. A lower bound is required so the query stays fast on
+            large projects; pair it with an upper bound to select a specific
+            window.
 
         fields : typing.Optional[str]
             Comma-separated list of field groups to include. Available groups:
@@ -205,7 +208,10 @@ def list_items(
         Parameters
         ----------
         from_start_time : dt.datetime
-            Retrieve only experiment items started on or after this datetime.
+            Required. Retrieve only experiment items started on or after this
+            datetime. A lower bound is required so the query stays fast on
+            large projects; pair it with an upper bound to select a specific
+            window.
 
         fields : typing.Optional[str]
             Comma-separated list of field groups to include. Available groups:
@@ -374,7 +380,10 @@ async def list(
         Parameters
         ----------
         from_start_time : dt.datetime
-            Retrieve only experiments on or after this datetime.
+            Required. Retrieve only experiments with events on or after this
+            datetime. A lower bound is required so the query stays fast on
+            large projects; pair it with an upper bound to select a specific
+            window.
 
         fields : typing.Optional[str]
             Comma-separated list of field groups to include. Available groups:
@@ -534,7 +543,10 @@ async def list_items(
         Parameters
         ----------
         from_start_time : dt.datetime
-            Retrieve only experiment items started on or after this datetime.
+            Required. Retrieve only experiment items started on or after this
+            datetime. A lower bound is required so the query stays fast on
+            large projects; pair it with an upper bound to select a specific
+            window.
 
         fields : typing.Optional[str]
             Comma-separated list of field groups to include. Available groups: