Issue: Dataset metadata parameter in create_dataset() not accessible via Dataset schema

[ashebensaadon]

Issue you'd like to raise.

Summary

The create_dataset() method accepts a metadata parameter, but the created dataset doesn't expose this metadata through the Dataset schema or any retrieval methods.

Expected Behavior

When creating a dataset with metadata:

from langsmith import Client

client = Client()
dataset = client.create_dataset(
    dataset_name="Test Dataset",
    description="Test dataset with metadata",
    metadata={"version": "1.0", "author": "test", "project": "my-project"}
)

# Should be able to access metadata
print(dataset.metadata)  # Expected: {"version": "1.0", "author": "test", "project": "my-project"}

Actual Behavior

• The create_dataset() method accepts the metadata parameter without error
• The returned Dataset object has no metadata attribute
• No way to retrieve the metadata that was passed during creation

Dataset Schema Fields

According to the [Dataset schema documentation, the Dataset class only includes:

• created_at
• example_count
• id
• inputs_schema
• last_session_start_time
• modified_at
• outputs_schema
• session_count
• url

Missing: metadata field

Environment

• LangSmith SDK version: 0.3.42
• Python version: 3.12.3

Code to Reproduce

from langsmith import Client

client = Client()

# This works without error
dataset = client.create_dataset(
    dataset_name="Test Dataset Metadata",
    description="Testing metadata functionality",
    metadata={"version": "1.0", "environment": "test"}
)

# This fails - no metadata attribute
try:
    print(dataset.metadata)
except AttributeError as e:
    print(f"AttributeError: {e}")

# This also doesn't show metadata
print(dataset.__dict__)

# Re-reading the dataset also doesn't show metadata
retrieved_dataset = client.read_dataset(dataset_name="Test Dataset Metadata")
print(f"Retrieved dataset attributes: {list(vars(retrieved_dataset).keys())}")

Possible Solutions

1. Add metadata field to Dataset schema and ensure it's returned when creating/reading datasets
2. Remove metadata parameter from create_dataset() if it's not intended to be supported
3. Add documentation clarifying the current status of dataset-level metadata support

Additional Context

• Example-level metadata works fine and is properly documented
• This creates confusion as the API accepts the parameter but provides no way to retrieve it
• Dataset description field works correctly

Documentation References

• [create_dataset method documentation](https://langsmith-sdk.readthedocs.io/en/latest/client/langsmith.client.Client.create_dataset.html) - shows metadata parameter
• [Dataset schema documentation](https://langsmith-sdk.readthedocs.io/en/latest/schemas/langsmith.schemas.Dataset.html) - no metadata field

Suggestion:

No response