diff --git a/agent/system_prompt.py b/agent/system_prompt.py
index 7d5bba76b3..64399226d5 100644
--- a/agent/system_prompt.py
+++ b/agent/system_prompt.py
@@ -415,7 +415,15 @@ def build_system_prompt_parts(agent: Any, system_message: Optional[str] = None)
 
     # Tool-aware behavioral guidance: only inject when the tools are loaded
     tool_guidance = []
-    if "memory" in agent.valid_tool_names:
+    # MEMORY_GUIDANCE instructs the model to save facts to the built-in
+    # MEMORY.md/USER.md stores. With both disabled in config no store is built,
+    # so the guidance would steer the model at a tool whose every call returns
+    # "Memory is not available". Defaults to True for the rare code paths that
+    # build an agent view without going through agent_init.
+    builtin_memory_active = getattr(agent, "_memory_enabled", True) or getattr(
+        agent, "_user_profile_enabled", True
+    )
+    if "memory" in agent.valid_tool_names and builtin_memory_active:
         tool_guidance.append(MEMORY_GUIDANCE)
     if "session_search" in agent.valid_tool_names:
         tool_guidance.append(SESSION_SEARCH_GUIDANCE)
diff --git a/tools/memory_tool.py b/tools/memory_tool.py
index 44effd02c2..c2ba72dc0e 100644
--- a/tools/memory_tool.py
+++ b/tools/memory_tool.py
@@ -1143,9 +1143,34 @@ def memory_tool(
     return json.dumps(result, ensure_ascii=False)
 
 
+def builtin_memory_stores_enabled() -> bool:
+    """Return whether either built-in store (MEMORY.md / USER.md) is enabled.
+
+    ``agent_init`` only builds a ``MemoryStore`` when at least one of
+    ``memory.memory_enabled`` / ``memory.user_profile_enabled`` is true, so with
+    both off the tool dispatches against ``store=None`` and every call fails
+    with "Memory is not available".
+
+    Fails open when config can't be read: an unreadable config must not strip a
+    tool that would otherwise work.
+    """
+    try:
+        from hermes_cli.config import load_config_readonly
+
+        section = (load_config_readonly() or {}).get("memory")
+        if not isinstance(section, dict):
+            return True
+        return bool(section.get("memory_enabled", True)) or bool(
+            section.get("user_profile_enabled", True)
+        )
+    except Exception:
+        logger.debug("Could not read memory config for availability", exc_info=True)
+        return True
+
+
 def check_memory_requirements() -> bool:
-    """Memory tool has no external requirements -- always available."""
-    return True
+    """Available unless both built-in memory stores are disabled in config."""
+    return builtin_memory_stores_enabled()
 
 
 def apply_memory_pending(payload: Dict[str, Any], store: "MemoryStore") -> Dict[str, Any]:
diff --git a/website/docs/user-guide/features/memory.md b/website/docs/user-guide/features/memory.md
index 624465821e..f76863da65 100644
--- a/website/docs/user-guide/features/memory.md
+++ b/website/docs/user-guide/features/memory.md
@@ -240,6 +240,15 @@ memory:
   write_approval: false     # false = write freely (default) | true = require approval
 ```
 
+Setting **both** `memory_enabled` and `user_profile_enabled` to `false` turns the
+built-in stores off completely: the `memory` tool is dropped from the schema and
+its guidance block is dropped from the system prompt, so the model is never told
+about a tool it cannot use. An external provider set via `memory.provider`
+(Hindsight, Mem0, Honcho, …) is unaffected and keeps its own tools — use this
+when you want a third-party memory backend *instead of* the built-in files.
+Listing `memory` under `agent.disabled_toolsets` is the heavier switch: it hides
+external provider tools too.
+
 ## Controlling memory writes (`write_approval`)
 
 By default the agent saves memory freely — including from the background