diff --git a/taskgen/agent.py b/taskgen/agent.py
index e892563..3191936 100644
--- a/taskgen/agent.py
+++ b/taskgen/agent.py
@@ -9,7 +9,7 @@
 import re
 import sys
 import base64
-from typing import Any, cast
+from typing import Any, Awaitable, Callable, Optional, Union, cast
 
 from termcolor import colored
 import requests
@@ -1235,11 +1235,20 @@ async def query(
         output_format: dict,
         provide_function_list: bool = False,
         task: str = "",
+        custom_validator: Optional[Callable[[Any], Union[Optional[str], Awaitable[Optional[str]]]]] = None,
     ):
         """Queries the agent with a query and outputs in output_format.
         If task is provided, we will filter the functions according to the task
         If you want to provide the agent with the context of functions available to it, set provide_function_list to True (default: False)
-        If task is given, then we will use it to do RAG over functions"""
+        If task is given, then we will use it to do RAG over functions
+
+        Optional validation + retry:
+            custom_validator: callable invoked with the LLM result. Returns None
+                if the result is acceptable, or a feedback string describing
+                what was wrong; the feedback is appended to the next prompt so
+                the LLM can self-correct within strict_json_async's retry budget.
+                May be sync or async.
+        """
 
         # if we have a task to focus on, we can filter the functions (other than use_llm and end_task) by that task
         filtered_fn_list = []
@@ -1258,6 +1267,7 @@ async def query(
             output_format=output_format,
             verbose=self.debug,
             llm=self.llm,
+            custom_validator=custom_validator,
             **self.kwargs,
         )
 
@@ -1770,4 +1780,4 @@ async def wrapper(*args, **kwargs):
         result = await method(*args, **all_kwargs)
         return result
 
-    return wrapper
\ No newline at end of file
+    return wrapper
diff --git a/taskgen/base_async.py b/taskgen/base_async.py
index 3a056da..a7e3c1a 100644
--- a/taskgen/base_async.py
+++ b/taskgen/base_async.py
@@ -1,8 +1,9 @@
 import asyncio
+import inspect
 import json
 import re
 import ast
-from typing import Tuple
+from typing import Any, Awaitable, Callable, Optional, Tuple, Union
 from taskgen.base import convert_to_dict, parse_response_llm_check, type_check_and_convert, wrap_with_angle_brackets
 
 from taskgen.utils import ensure_awaitable
@@ -229,7 +230,19 @@ async def chat_async(system_prompt: str, user_prompt: str|list[str|dict], model:
 ### Main Functions ###
     
     
-async def strict_json_async(system_prompt: str, user_prompt: str|list[str|dict], output_format: dict, return_as_json = False, custom_checks: dict|None = None, check_data = None, delimiter: str = '###', num_tries: int = 3, openai_json_mode: bool = False, **kwargs):
+async def strict_json_async(
+    system_prompt: str,
+    user_prompt: str|list[str|dict],
+    output_format: dict,
+    return_as_json = False,
+    custom_checks: dict|None = None,
+    check_data = None,
+    delimiter: str = '###',
+    num_tries: int = 3,
+    openai_json_mode: bool = False,
+    custom_validator: Optional[Callable[[Any], Union[Optional[str], Awaitable[Optional[str]]]]] = None,
+    **kwargs
+):
     r""" Ensures that OpenAI will always adhere to the desired output JSON format defined in output_format.
     Uses rule-based iterative feedback to ask GPT to self-correct.
     Keeps trying up to num_tries it it does not. Returns empty JSON if unable to after num_tries iterations.
@@ -246,6 +259,8 @@ async def strict_json_async(system_prompt: str, user_prompt: str|list[str|dict],
     - delimiter: String (Default: '###'). This is the delimiter to surround the keys. With delimiter ###, key becomes ###key###
     - num_tries: Integer (default: 3). The number of tries to iteratively prompt GPT to generate correct json format
     - openai_json_mode: Boolean (default: False). Whether or not to use OpenAI JSON Mode
+    - custom_validator: Optional callable invoked with the parsed output. Returns None if valid,
+      or a feedback string describing what to fix. May be sync or async.
     - **kwargs: Dict. Additional arguments for LLM chat
     
     Output:
@@ -348,6 +363,13 @@ async def strict_json_async(system_prompt: str, user_prompt: str|list[str|dict],
                                 raise Exception(f'Output field of "{key}" does not meet requirement "{requirement}". Action needed: "{action_needed}"')
                             else:
                                 print('Requirement met\n\n')
+                if custom_validator is not None:
+                    feedback = custom_validator(end_dict)
+                    if inspect.isawaitable(feedback):
+                        feedback = await feedback
+                    if feedback:
+                        print(f'Custom validator rejected output. Action needed: "{feedback}"\n\n')
+                        raise Exception(f'Output does not meet custom validator requirement. Action needed: "{feedback}"')
                 if return_as_json:
                     return json.dumps(end_dict, ensure_ascii=False)
                 else:
@@ -363,4 +385,4 @@ async def strict_json_async(system_prompt: str, user_prompt: str|list[str|dict],
 ### Legacy Support ###
 # alternative names for strict_json
 strict_text_async = strict_json_async
-strict_output_async = strict_json_async
\ No newline at end of file
+strict_output_async = strict_json_async