Structured Output Compliance | Opik Documentation

The StructuredOutputCompliance metric allows you to verify whether a given LLM output is valid JSON and adheres to an expected schema. You can optionally provide a Pydantic schema to validate the structure and types of the fields.

How to use the StructuredOutputCompliance metric

You can use the StructuredOutputCompliance metric as follows:

from opik.evaluation.metrics import StructuredOutputCompliance
from pydantic import BaseModel, Field
class User(BaseModel):
    name: str = Field(description="The name of the user")
    age: int = Field(description="The age of the user")
metric = StructuredOutputCompliance()
# Example 1: Valid JSON, but not schema-compliant
metric.score(
    output='{"name": "John Doe"}',
    schema=User,
)
# Example 2: Valid JSON and schema-compliant
metric.score(
    output='{"name": "John Doe", "age": 30}',
    schema=User,
)
# Example 3: Invalid JSON
metric.score(
    output='{"name": "John Doe", "age": }',
)

Asynchronous scoring is also supported with the ascore method.

The StructuredOutputCompliance score is 1 if the output is compliant, and 0 if it is not.

Prompt Template

Opik uses an LLM as a Judge to evaluate the structural compliance. The default model used is gpt-4o, but this can be changed to any model supported by LiteLLM.

The prompt used by the LLM looks like this:

You are an expert in structured data validation. Your task is to determine whether the given OUTPUT complies with the expected STRUCTURE. The structure may be described as a JSON schema, a Pydantic model, or simply implied to be valid JSON.
Guidelines:
1. OUTPUT must be a valid JSON object (not just a string).
2. If a schema is provided, the OUTPUT must match the schema exactly in field names, types, and structure.
3. If no schema is provided, ensure the OUTPUT is a well-formed and parsable JSON.
4. Common formatting issues (missing quotes, incorrect brackets, etc.) should be flagged.
5. Partial compliance is considered non-compliant.
6. Respond only in the specified JSON format.
{examples_str}
EXPECTED STRUCTURE (optional):
{schema}
OUTPUT:
{output}
Respond in the following JSON format:
{{
    "score": true or false,  // true if output fully complies, false otherwise
    "reason": ["list of reasons for failure or confirmation"]
}}