diff --git a/lib/crewai/src/crewai/a2a/config.py b/lib/crewai/src/crewai/a2a/config.py
index 499248046..51c5c4adc 100644
--- a/lib/crewai/src/crewai/a2a/config.py
+++ b/lib/crewai/src/crewai/a2a/config.py
@@ -16,6 +16,7 @@ from pydantic import (
     FilePath,
     PrivateAttr,
     SecretStr,
+    field_serializer,
     model_validator,
 )
 from typing_extensions import Self, deprecated
@@ -24,6 +25,7 @@ from crewai.a2a.auth.client_schemes import ClientAuthScheme
 from crewai.a2a.auth.server_schemes import ServerAuthScheme
 from crewai.a2a.extensions.base import ValidatedA2AExtension
 from crewai.a2a.types import ProtocolVersion, TransportType, Url
+from crewai.utilities.pydantic_schema_utils import serialize_model_class
 
 
 try:
@@ -399,6 +401,11 @@ class A2AConfig(BaseModel):
         default=None,
         description="Optional Pydantic model for structured A2A agent responses",
     )
+
+    @field_serializer("response_model", when_used="json")
+    def _serialize_response_model(self, value: Any) -> Any:
+        return serialize_model_class(value)
+
     fail_fast: bool = Field(
         default=True,
         description="If True, raise error when agent unreachable; if False, skip",
@@ -488,6 +495,11 @@ class A2AClientConfig(BaseModel):
         default=None,
         description="Optional Pydantic model for structured A2A agent responses",
     )
+
+    @field_serializer("response_model", when_used="json")
+    def _serialize_response_model(self, value: Any) -> Any:
+        return serialize_model_class(value)
+
     fail_fast: bool = Field(
         default=True,
         description="If True, raise error when agent unreachable; if False, skip",
diff --git a/lib/crewai/src/crewai/lite_agent.py b/lib/crewai/src/crewai/lite_agent.py
index cd9823e15..3aff8ea35 100644
--- a/lib/crewai/src/crewai/lite_agent.py
+++ b/lib/crewai/src/crewai/lite_agent.py
@@ -23,6 +23,7 @@ from pydantic import (
     BaseModel,
     Field,
     PrivateAttr,
+    field_serializer,
     field_validator,
     model_validator,
 )
@@ -94,7 +95,10 @@ from crewai.utilities.guardrail import process_guardrail, serialize_guardrail_fo
 from crewai.utilities.guardrail_types import GuardrailCallable, GuardrailType
 from crewai.utilities.i18n import I18N_DEFAULT
 from crewai.utilities.llm_utils import create_llm
-from crewai.utilities.pydantic_schema_utils import generate_model_description
+from crewai.utilities.pydantic_schema_utils import (
+    generate_model_description,
+    serialize_model_class,
+)
 from crewai.utilities.token_counter_callback import TokenCalcHandler
 from crewai.utilities.tool_utils import execute_tool_and_check_finality
 from crewai.utilities.types import LLMMessage
@@ -235,6 +239,11 @@ class LiteAgent(FlowTrackable, BaseModel):
     response_format: type[BaseModel] | None = Field(
         default=None, description="Pydantic model for structured output"
     )
+
+    @field_serializer("response_format", when_used="json")
+    def _serialize_response_format(self, value: Any) -> Any:
+        return serialize_model_class(value)
+
     verbose: bool = Field(
         default=False, description="Whether to print execution details"
     )
diff --git a/lib/crewai/src/crewai/llms/base_llm.py b/lib/crewai/src/crewai/llms/base_llm.py
index 8c2993d3a..3e6c4f828 100644
--- a/lib/crewai/src/crewai/llms/base_llm.py
+++ b/lib/crewai/src/crewai/llms/base_llm.py
@@ -23,6 +23,7 @@ from pydantic import (
     ConfigDict,
     Field,
     PrivateAttr,
+    field_serializer,
     model_validator,
 )
 from typing_extensions import TypedDict
@@ -42,6 +43,7 @@ from crewai.events.types.tool_usage_events import (
     ToolUsageStartedEvent,
 )
 from crewai.types.usage_metrics import UsageMetrics
+from crewai.utilities.pydantic_schema_utils import serialize_model_class
 
 
 try:
@@ -159,6 +161,10 @@ class BaseLLM(BaseModel, ABC):
     )
     additional_params: dict[str, Any] = Field(default_factory=dict)
 
+    @field_serializer("response_format", when_used="json", check_fields=False)
+    def _serialize_response_format(self, value: Any) -> Any:
+        return serialize_model_class(value)
+
     def __setattr__(self, name: str, value: Any) -> None:
         if name in ("stop", "stop_sequences"):
             if value is None:
diff --git a/lib/crewai/src/crewai/tools/base_tool.py b/lib/crewai/src/crewai/tools/base_tool.py
index e1dc8f2ee..31c5009bd 100644
--- a/lib/crewai/src/crewai/tools/base_tool.py
+++ b/lib/crewai/src/crewai/tools/base_tool.py
@@ -8,7 +8,6 @@ from inspect import Parameter, signature
 import json
 import threading
 from typing import (
-    Annotated,
     Any,
     Generic,
     ParamSpec,
@@ -22,10 +21,10 @@ from pydantic import (
     ConfigDict,
     Field,
     GetCoreSchemaHandler,
-    PlainSerializer,
     PrivateAttr,
     computed_field,
     create_model,
+    field_serializer,
     field_validator,
 )
 from pydantic_core import CoreSchema, core_schema
@@ -145,15 +144,18 @@ class BaseTool(BaseModel, ABC):
         default_factory=list,
         description="List of environment variables used by the tool.",
     )
-    args_schema: Annotated[
-        type[PydanticBaseModel],
-        PlainSerializer(_serialize_schema, return_type=dict | None, when_used="json"),
-    ] = Field(
+    args_schema: type[PydanticBaseModel] = Field(
         default=_ArgsSchemaPlaceholder,
         validate_default=True,
         description="The schema for the arguments that the tool accepts.",
     )
 
+    @field_serializer("args_schema", when_used="json")
+    def _serialize_args_schema(
+        self, schema: type[PydanticBaseModel] | None
+    ) -> dict[str, Any] | None:
+        return _serialize_schema(schema)
+
     description_updated: bool = Field(
         default=False, description="Flag to check if the description has been updated."
     )
diff --git a/lib/crewai/src/crewai/utilities/pydantic_schema_utils.py b/lib/crewai/src/crewai/utilities/pydantic_schema_utils.py
index a45c1635a..ff1d5529b 100644
--- a/lib/crewai/src/crewai/utilities/pydantic_schema_utils.py
+++ b/lib/crewai/src/crewai/utilities/pydantic_schema_utils.py
@@ -782,6 +782,20 @@ def _inline_top_level_ref(schema: dict[str, Any]) -> dict[str, Any]:
     return schema
 
 
+def serialize_model_class(value: Any) -> Any:
+    """Serialize a ``type[BaseModel]`` field value as its JSON schema.
+
+    Args:
+        value: A ``type[BaseModel]`` subclass, ``None``, or another union member.
+
+    Returns:
+        ``value.model_json_schema()`` for model classes, ``value`` otherwise.
+    """
+    if isinstance(value, type) and issubclass(value, BaseModel):
+        return value.model_json_schema()
+    return value
+
+
 def create_model_from_schema(  # type: ignore[no-any-unimported]
     json_schema: dict[str, Any],
     *,