diff --git a/core/requirements.txt b/core/requirements.txt
index 2f5e1fd..6a6395f 100644
--- a/core/requirements.txt
+++ b/core/requirements.txt
@@ -11,4 +11,5 @@ presidio-analyzer>=2.2,<3.0
 presidio-anonymizer>=2.2,<3.0
 openai>=1.50,<2.0
 PyYAML>=6.0,<7.0
+jsonschema>=4.0,<5.0
 nemoguardrails>=0.10,<0.12
diff --git a/core/src/agentforge_core/guardrails/base.py b/core/src/agentforge_core/guardrails/base.py
new file mode 100644
index 0000000..36c8dd5
--- /dev/null
+++ b/core/src/agentforge_core/guardrails/base.py
@@ -0,0 +1,29 @@
+"""Interfaz Protocol del motor de guardrails."""
+
+from __future__ import annotations
+
+from typing import Any, Protocol
+from uuid import UUID
+
+from agentforge_core.domain.guardrail import GuardrailViolation
+from agentforge_core.domain.policy import PolicyDefinition
+
+
+class GuardrailEngine(Protocol):
+    """Motor de validación. Las violaciones se devuelven; el grafo decide bloquear."""
+
+    name: str
+
+    async def validate_input(
+        self,
+        payload: str,
+        policy: PolicyDefinition,
+        trace_id: UUID,
+    ) -> list[GuardrailViolation]: ...
+
+    async def validate_output(
+        self,
+        payload: dict[str, Any],
+        policy: PolicyDefinition,
+        trace_id: UUID,
+    ) -> list[GuardrailViolation]: ...