diff --git a/just_agents/cot_agent.py b/just_agents/cot_agent.py
index e08d88c..204be1d 100644
--- a/just_agents/cot_agent.py
+++ b/just_agents/cot_agent.py
@@ -4,7 +4,7 @@
 from just_agents.streaming.protocols.openai_streaming import OpenaiStreamingProtocol
 from just_agents.streaming.protocols.abstract_protocol import AbstractStreamingProtocol
 from pathlib import Path
-from just_agents.utils import _resolve_agent_schema, resolve_llm_options, resolve_system_prompt, resolve_tools
+from just_agents.utils import resolve_and_validate_agent_schema, resolve_llm_options, resolve_system_prompt, resolve_tools
 
 # schema parameters:
 LLM_SESSION = "llm_session"
@@ -21,7 +21,7 @@ class ChainOfThoughtAgent(IAgent):
 
     def __init__(self, llm_options: dict = None, agent_schema: str | Path | dict | None = None,
                  tools: list = None, output_streaming:AbstractStreamingProtocol = OpenaiStreamingProtocol()):
-        self.agent_schema: dict = _resolve_agent_schema(agent_schema, "cot_agent_prompt.yaml")
+        self.agent_schema: dict = resolve_and_validate_agent_schema(agent_schema, "cot_agent_prompt.yaml")
         if tools is None:
             tools = resolve_tools(self.agent_schema)
         self.session: LLMSession = LLMSession(llm_options=resolve_llm_options(self.agent_schema, llm_options),
diff --git a/just_agents/llm_session.py b/just_agents/llm_session.py
index f503de4..b9759fb 100644
--- a/just_agents/llm_session.py
+++ b/just_agents/llm_session.py
@@ -15,7 +15,7 @@
 from just_agents.streaming.abstract_streaming import AbstractStreaming
 from just_agents.streaming.openai_streaming import AsyncSession
 # from just_agents.utils import rotate_completion
-from just_agents.utils import _resolve_agent_schema, resolve_llm_options, resolve_system_prompt, resolve_tools
+from just_agents.utils import resolve_and_validate_agent_schema, resolve_llm_options, resolve_system_prompt, resolve_tools
 from just_agents.rotate_keys import RotateKeys
 
 OnCompletion = Callable[[ModelResponse], None]
@@ -46,7 +46,7 @@ def __init__(self, llm_options: dict[str, Any] = None,
         self.key_getter: RotateKeys = None
         self.on_response: list[OnCompletion] = []
 
-        self.agent_schema = _resolve_agent_schema(agent_schema, "llm_session_schema.yaml")
+        self.agent_schema = resolve_and_validate_agent_schema(agent_schema, "llm_session_schema.yaml")
         self.llm_options: dict[str, Any] = resolve_llm_options(self.agent_schema, llm_options)
         if self.agent_schema.get(KEY_LIST_PATH, None) is not None:
             self.key_getter = RotateKeys(self.agent_schema[KEY_LIST_PATH])
diff --git a/just_agents/utils.py b/just_agents/utils.py
index 0bcc1fe..702ac5a 100644
--- a/just_agents/utils.py
+++ b/just_agents/utils.py
@@ -8,26 +8,11 @@
 from dotenv import load_dotenv
 import importlib
 from typing import Callable
-from litellm import Message, ModelResponse, completion
-import copy
-
-#
-# class RotateKeys():
-#     keys:list[str]
-#
-#     def __init__(self, file_path:str):
-#         with open(file_path) as f:
-#             text = f.read().strip()
-#             self.keys = text.split("\n")
-#
-#     def __call__(self, *args, **kwargs):
-#         return random.choice(self.keys)
-#
-#     def remove(self, key:str):
-#         self.keys.remove(key)
-#
-#     def len(self):
-#         return len(self.keys)
+
+class SchemaValidationError(ValueError):
+    pass
+
+VALIDATION_EXTRAS = ["package", "function"]
 
 def resolve_agent_schema(agent_schema: str | Path | dict):
     """
@@ -47,11 +32,36 @@ def resolve_agent_schema(agent_schema: str | Path | dict):
 
     return agent_schema
 
-def _resolve_agent_schema(agent_schema: str | Path | dict | None, default_file_name: str):
+def resolve_and_validate_agent_schema(agent_schema: str | Path | dict | None, default_file_name: str):
+    reference_schema = resolve_agent_schema(Path(Path(__file__).parent, "config", default_file_name))
     if agent_schema is None:
-        agent_schema = Path(Path(__file__).parent, "config", default_file_name)
+        return reference_schema
+
+    agent_schema = resolve_agent_schema(agent_schema)
+    validate_schema(reference_schema, agent_schema)
+
+    return agent_schema
+
+
+def create_fields_set(source: dict[str, Any], fields_set: set[str]):
+    for key in source:
+        fields_set.add(key)
+        if isinstance(source[key], dict):
+            create_fields_set(source[key], fields_set)
+
+
+def validate_schema(reference: dict[str, Any], schema: dict[str, Any]):
+    reference_set: set[str] = set(VALIDATION_EXTRAS)
+    schema_set: set[str] = set()
+    create_fields_set(reference, reference_set)
+    create_fields_set(schema, schema_set)
+    error_fields = []
+    for field in schema_set:
+        if field not in reference_set:
+            error_fields.append(field)
 
-    return resolve_agent_schema(agent_schema)
+    if len(error_fields) > 0:
+        raise SchemaValidationError(f" Fields {error_fields} not exists in yaml schema. Choose from {reference_set}")
 
 
 def resolve_llm_options(agent_schema: dict, llm_options: dict):
diff --git a/tests/test_yaml_validator.py b/tests/test_yaml_validator.py
new file mode 100644
index 0000000..70640ba
--- /dev/null
+++ b/tests/test_yaml_validator.py
@@ -0,0 +1,9 @@
+from just_agents.interfaces.IAgent import build_agent
+from just_agents.utils import SchemaValidationError
+
+def test_yaml_validator():
+    try:
+        agent = build_agent("wrong_yaml.yaml")
+    except SchemaValidationError as e:
+        assert "jus_streming_method" in str(e)
+        assert "backup_optionss" in str(e)
\ No newline at end of file
diff --git a/tests/wrong_yaml.yaml b/tests/wrong_yaml.yaml
new file mode 100644
index 0000000..7e9fb76
--- /dev/null
+++ b/tests/wrong_yaml.yaml
@@ -0,0 +1,10 @@
+class: "LLMSession" # class name to create could be LLMSession, ChainOfThoughtAgent. Default is LLMSession
+jus_streming_method: "openai" # protocol to handle llm format for function calling
+system_prompt: # system prompt exclude use of system_prompt_path
+completion_max_tries: 2 # maximum number of completion retries before giving up
+backup_optionss: # options that will be used after we give up with main options, one more completion call will be done with backup options
+key_list_path: # path to text file with list of api keys, one key per line
+tools: # list of functions that will be used as tools, each record should contain package and function name
+drop_params: True # drop params from the request, useful for some models that do not support them
+#  - package:
+#    function:
\ No newline at end of file