Use request tags in Unity Gateway service policies

Use cases

Imagine you need to ensure that calls to an AI model or MCP tool include a valid project identifier before proceeding. With this feature, you can inspect caller-supplied tags directly within SQL-based service policies.

• Validate project or cost center tags before executing a model or tool.
• Block requests that lack required metadata tags.
• Enforce governance rules based on request context.

How to use

Use the Unity Gateway to create a SQL UDF that evaluates the event object and returns an access decision.

CREATE OR REPLACE FUNCTION my_catalog.my_schema.my_policy(
  event VARIANT
)
RETURNS VARIANT
LANGUAGE SQL
RETURN CASE 
  WHEN event:context.request_tags.project::string IS NULL THEN 
    to_variant_object(named_struct('result', 'DENY', 'reason', 'Required project tag is missing.'))
  ELSE 
    to_variant_object(named_struct('result', 'ALLOW', 'reason', 'Access permitted.'))
END;

What happens in this code:

1. The UDF function receives the event argument of type VARIANT carrying the request context.
2. The path event:context.request_tags.project extracts the tag sent in the Databricks-Ai-Gateway-Request-Tags HTTP header.
3. The conditional evaluates if the tag is present and returns a structured decision object using to_variant_object containing ALLOW or DENY.

Limitations and requirements

• This feature is in Beta.
• Applies to Model Services, Model Provider Services, and MCP tool calls (tools/call).
• The combined decoded size of keys and values is limited to 10 KiB of UTF-8 data.
• Account admins must enable this feature from the account console Previews page.