diff --git a/src/basic_memory/mcp/tools/edit_note.py b/src/basic_memory/mcp/tools/edit_note.py
index 7d483ef1..eedaea3b 100644
--- a/src/basic_memory/mcp/tools/edit_note.py
+++ b/src/basic_memory/mcp/tools/edit_note.py
@@ -135,7 +135,7 @@ async def edit_note(
     workspace: Optional[str] = None,
     section: Optional[str] = None,
     find_text: Optional[str] = None,
-    expected_replacements: int = 1,
+    expected_replacements: Optional[int] = None,
     output_format: Literal["text", "json"] = "text",
     context: Context | None = None,
 ) -> str | dict:
@@ -216,6 +216,9 @@ async def edit_note(
         search_notes() first to find the correct identifier. The tool provides detailed
         error messages with suggestions if operations fail.
     """
+    # Resolve effective default: allow MCP clients to send null for optional int field
+    effective_replacements = expected_replacements if expected_replacements is not None else 1
+
     async with get_project_client(project, workspace, context) as (client, active_project):
         logger.info("MCP tool call", tool="edit_note", identifier=identifier, operation=operation)
 
@@ -254,8 +257,8 @@ async def edit_note(
                 edit_data["section"] = section
             if find_text:
                 edit_data["find_text"] = find_text
-            if expected_replacements != 1:  # Only send if different from default
-                edit_data["expected_replacements"] = str(expected_replacements)
+            if effective_replacements != 1:  # Only send if different from default
+                edit_data["expected_replacements"] = str(effective_replacements)
 
             # Call the PATCH endpoint
             result = await knowledge_client.patch_entity(entity_id, edit_data, fast=False)
@@ -339,5 +342,5 @@ async def edit_note(
                     "error": str(e),
                 }
             return _format_error_response(
-                str(e), operation, identifier, find_text, expected_replacements, active_project.name
+                str(e), operation, identifier, find_text, effective_replacements, active_project.name
             )
diff --git a/tests/mcp/test_tool_edit_note.py b/tests/mcp/test_tool_edit_note.py
index 84f53a64..5f2f3f9f 100644
--- a/tests/mcp/test_tool_edit_note.py
+++ b/tests/mcp/test_tool_edit_note.py
@@ -414,6 +414,39 @@ async def test_edit_note_find_replace_empty_find_text(client, test_project):
     # Should contain helpful guidance about the error
 
 
+@pytest.mark.asyncio
+async def test_edit_note_append_with_null_optional_fields(client, test_project):
+    """Regression test: MCP clients may send explicit null for unused optional fields.
+
+    When an MCP client sends find_text=None, section=None, expected_replacements=None
+    for an append operation, the tool should accept them without validation errors.
+    """
+    # Create initial note
+    await write_note(
+        project=test_project.name,
+        title="Null Fields Test",
+        directory="test",
+        content="# Null Fields Test\nOriginal content.",
+    )
+
+    # Call edit_note with explicit None for all optional fields (simulates MCP null)
+    result = await edit_note(
+        project=test_project.name,
+        identifier="test/null-fields-test",
+        operation="append",
+        content="\nAppended content.",
+        find_text=None,
+        section=None,
+        expected_replacements=None,
+    )
+
+    assert isinstance(result, str)
+    assert "Edited note (append)" in result
+    assert f"project: {test_project.name}" in result
+    assert "file_path: test/Null Fields Test.md" in result
+    assert f"[Session: Using project '{test_project.name}']" in result
+
+
 @pytest.mark.asyncio
 async def test_edit_note_preserves_permalink_when_frontmatter_missing(client, test_project):
     """Test that editing a note preserves the permalink when frontmatter doesn't contain one.