fix: Add default name property to node types defined without a properties key (#499)

* Add default prop

* Update changelog

* Fix mypy errors

* Update user guide

Author: ali-sedaghatbaf

CHANGELOG.md

@@ -6,6 +6,10 @@
 
 - MarkdownLoader (experimental): added a Markdown loader to support `.md` and `.markdown` files.
 
+### Fixed
+
+- `NodeType`: a node type defined without a `properties` key (e.g. `{"label": "Person"}` or `{"label": "Person", "description": "..."}`) now automatically gets a default `name: STRING` property and `additional_properties=True`, preventing a `ValidationError` from the `min_length=1` constraint. This matches the existing behaviour for string input. Auto-addition is skipped when `properties` is explicitly provided (including as an empty list) or when `additional_properties` is explicitly set to `False`.
+
 ### Changed
 
 - SimpleKG pipeline (experimental): the `from_pdf` parameter is deprecated in favor of `from_file` (PDF and Markdown inputs). `from_pdf` still works but emits a deprecation warning and will be removed in a future version.

docs/source/user_guide_kg_builder.rst

@@ -79,18 +79,18 @@ with, optionally, a list of their expected properties)
 and instructions on how to connect them (patterns).
 Node and relationship types can be represented
 as either simple strings (for their labels) or dictionaries. If using a dictionary,
-it must include a label key and can optionally include description and properties keys,
+it must include a ``label`` key and can optionally include ``description`` and ``properties`` keys,
 as shown below:
 
 .. code:: python
 
     NODE_TYPES = [
-        # node types can be defined with a simple label...
+        # node types can be defined with a simple label string...
         "Person",
-        # ... or with a dict if more details are needed,
-        # such as a description:
+        # ... or with a dict for more detail such as a description.
+        # When no properties key is provided, a default "name" property is added automatically.
         {"label": "House", "description": "Family the person belongs to"},
-        # or a list of properties the LLM will try to attach to the entity:
+        # or with an explicit list of properties the LLM will try to attach to the entity:
         {"label": "Planet", "properties": [{"name": "name", "type": "STRING", "required": True}, {"name": "weather", "type": "STRING"}]},
     ]
     # same thing for relationships:
@@ -912,19 +912,32 @@ For improved reliability with :ref:`OpenAILLM <openaillm>` or :ref:`VertexAILLM
 Schema Validation and Node Properties
 --------------------------------------
 
-**Important:** All node types must have at least one property defined. When using string shorthand for node types (e.g., ``"Person"``), a default ``"name"`` property is automatically added with ``additional_properties=True`` to allow flexible LLM extraction:
+All node types must have at least one property defined. When no properties are provided,
+a default ``name: STRING`` property is added automatically and ``additional_properties``
+is set to ``True`` to allow the LLM to extract additional properties freely.
+
+This applies to both the **string shorthand** and the **long dict syntax** when the
+``properties`` key is omitted:
 
 .. code:: python
 
-    # String shorthand - automatically gets default property
-    NodeType("Person")  # Becomes: properties=[{"name": "name", "type": "STRING"}], additional_properties=True
-    
-    # Explicit definition - must include at least one property
-    NodeType(
-        label="Person",
-        properties=[PropertyType(name="name", type="STRING")],
-        additional_properties=True  # Allow LLM to extract additional properties
-    )
+    # String shorthand — "name" property added automatically
+    "Person"
+    # equivalent to:
+    NodeType(label="Person", properties=[PropertyType(name="name", type="STRING")], additional_properties=True)
+
+    # Long syntax without a properties key — same auto-addition applies
+    {"label": "House", "description": "Family the person belongs to"}
+    # equivalent to:
+    NodeType(label="House", description="Family the person belongs to",
+             properties=[PropertyType(name="name", type="STRING")], additional_properties=True)
+
+Passing ``properties`` explicitly as an empty list raises a ``ValidationError``:
+
+.. code:: python
+
+    # Raises ValidationError — empty list is not auto-filled
+    {"label": "House", "properties": []}
 
 **Relationship types** with no properties automatically set ``additional_properties=True`` to preserve LLM-extracted properties during graph construction.
 

src/neo4j_graphrag/experimental/components/schema.py

@@ -15,54 +15,52 @@
 from __future__ import annotations
 
 import json
-import re
-
-import neo4j
 import logging
+import re
 import warnings
+from pathlib import Path
 from typing import (
     Any,
+    Callable,
     Dict,
     Iterator,
     List,
     Literal,
     Optional,
+    Sequence,
     Tuple,
     Union,
-    Sequence,
-    Callable,
     cast,
 )
-from pathlib import Path
 
+import neo4j
 from pydantic import (
     BaseModel,
+    ConfigDict,
+    Field,
     PrivateAttr,
+    ValidationError,
     field_validator,
     model_validator,
     validate_call,
-    ConfigDict,
-    ValidationError,
-    Field,
 )
 from typing_extensions import Self
 
 from neo4j_graphrag.exceptions import (
-    SchemaValidationError,
     LLMGenerationError,
     SchemaExtractionError,
+    SchemaValidationError,
 )
 from neo4j_graphrag.experimental.pipeline.component import Component, DataModel
 from neo4j_graphrag.experimental.pipeline.types.schema import (
     EntityInputType,
     RelationInputType,
 )
-from neo4j_graphrag.generation import SchemaExtractionTemplate, PromptTemplate
+from neo4j_graphrag.generation import PromptTemplate, SchemaExtractionTemplate
 from neo4j_graphrag.llm import LLMInterface
-from neo4j_graphrag.types import LLMMessage
-from neo4j_graphrag.utils.file_handler import FileHandler, FileFormat
 from neo4j_graphrag.schema import get_structured_schema
-
+from neo4j_graphrag.types import LLMMessage
+from neo4j_graphrag.utils.file_handler import FileFormat, FileHandler
 
 logger = logging.getLogger(__name__)
 
@@ -146,6 +144,23 @@ def validate_input_if_string(cls, data: EntityInputType) -> EntityInputType:
                 # allow LLM to extract additional properties beyond the default "name"
                 "additional_properties": True,  # type: ignore[dict-item]
             }
+        if isinstance(data, dict) and "properties" not in data:
+            if data.get("additional_properties") is False:  # type: ignore[comparison-overlap]
+                return data
+            label = data.get("label", "")
+            logger.info(
+                f"No properties defined for NodeType '{label}'. "
+                f"Adding default 'name' property and additional_properties=True "
+                f"to allow flexible property extraction."
+            )
+            return {
+                **data,
+                # added to satisfy the model validation (min_length=1 for properties of node types)
+                "properties": [{"name": "name", "type": "STRING"}],
+                # allow LLM to extract additional properties beyond the default "name"
+                "additional_properties": True,  # type: ignore[dict-item]
+            }
+
         return data
 
     @model_validator(mode="after")