rubric 2.2.0

Rubric: A Python library for LLM-based evaluation using weighted rubrics.

Installation

uv add rubric

Usage

Quick Start with Default Generate Functions

For quick testing, use the built-in Gemini generate functions:

export GEMINI_API_KEY=your_api_key_here

import asyncio
from rubric import Rubric, default_per_criterion_generate_fn
from rubric.autograders import PerCriterionGrader

async def main():
    rubric = Rubric.from_dict([
        {"weight": 10.0, "requirement": "Response mentions Paris"},
        {"weight": 5.0, "requirement": "Response is concise"}
    ])

    grader = PerCriterionGrader(generate_fn=default_per_criterion_generate_fn)
    result = await rubric.grade("Paris is the capital of France.", autograder=grader)
    print(f"Score: {result.score}")

asyncio.run(main())

See examples/basic_usage.py for more examples with all three autograder types.

Custom Generate Function with OpenAI

For production use, implement your own generate_fn with structured outputs:

import asyncio
import os
from openai import AsyncOpenAI
from rubric import Rubric, PerCriterionOutput
from rubric.autograders import PerCriterionGrader

# Declare custom generate function with any model and inference provider
async def generate_with_openai(system_prompt: str, user_prompt: str) -> PerCriterionOutput:
    client = AsyncOpenAI(api_key=os.getenv("OPENAI_API_KEY"))
    response = await client.chat.completions.create(
        model="gpt-5-mini",
        messages=[
            {"role": "system", "content": system_prompt},
            {"role": "user", "content": user_prompt},
        ],
        response_format={"type": "json_schema", "json_schema": {
            "name": "criterion_output",
            "schema": PerCriterionOutput.model_json_schema()
        }},
        max_tokens=400,
        temperature=0.0,
    )
    content = response.choices[0].message.content or "{}"
    return PerCriterionOutput.model_validate_json(content)

async def main():
    # Build rubric
    rubric = Rubric.from_dict([
        {"weight": 10.0, "requirement": "States Q4 2023 base margin as 17.2%"},
        {"weight": 8.0, "requirement": "Explicitly uses Shapley attribution for decomposition"},
        {"weight": -15.0, "requirement": "Uses total deliveries instead of cash-only deliveries"}
    ])

    # Select autograder strategy
    grader = PerCriterionGrader(
        generate_fn=generate_with_openai,
        normalize=False,  # Raw weighted sums
        system_prompt="This overrides the default grader system prompt",
    )

    # Grade output
    result = await rubric.grade(
        query="Input query...",
        to_grade="Output to evaluate...",
        autograder=grader
    )

    print(f"Score: {result.score:.2f}")  # Raw weighted sum
    for criterion in result.report:
        print(f"  [{criterion.verdict}] {criterion.requirement}")
        print(f"    → {criterion.reason}")

asyncio.run(main())

Autograder Strategies

PerCriterionGrader

Evaluates each criterion in parallel inference calls.

Scoring Formula:

For each criterion $i$: MET contributes $w_i$, UNMET contributes 0.

Raw score:

$$ \texttt{raw\score} = \sum{i=1}^{n} \mathbb{1}[\text{verdict}_i = \text{MET}] \cdot w_i $$

Normalized score (normalize=True, the default):

$$ \texttt{score} = \max\left(0, \min\left(1, \frac{\texttt{raw\score}}{\sum{i=1}^{n} \max(0, w_i)}\right)\right) $$

Pass normalize=False to the autograder constructor for raw weighted sums.

All-Negative Criteria Rubrics:

For rubrics with only negative criteria (e.g., error detection):

Raw score: Same formula as above. Will be ≤ 0 since all weights are negative.

Normalized score (default):

$$ \texttt{score} = \max\left(0, \min\left(1, 1 + \frac{\texttt{raw\score}}{\sum{i=1}^{n} |w_i|}\right)\right) $$

Score = 1.0 when all errors avoided (all UNMET, raw_score = 0) Score = 0.0 when all errors present (all MET, raw_score = -total)

PerCriterionOneShotGrader

Makes 1 inference call for all criteria (vs. $n$ parallel calls). Same scoring as PerCriterionGrader:

Raw score:

$$ \texttt{raw\score} = \sum{i=1}^{n} \mathbb{1}[\text{verdict}_i = \text{MET}] \cdot w_i $$

Normalized score (normalize=True, the default):

$$ \texttt{score} = \max\left(0, \min\left(1, \frac{\texttt{raw\score}}{\sum{i=1}^{n} \max(0, w_i)}\right)\right) $$

RubricAsJudgeGrader

Holistic evaluation where the model returns a single 0-100 score.

LLM raw score: The model's direct 0-100 output, preserved in llm_raw_score.

Raw score (converted to weighted-sum for cross-grader consistency):

$$ \texttt{raw\_score} = \frac{\texttt{llm\_raw\score}}{100} \times \sum{i=1}^{n} \max(0, w_i) $$

Normalized score (normalize=True, default): $\texttt{score} = \max(0, \min(1, \texttt{llm\_raw\_score} / 100))$

Unnormalized score (normalize=False): $\texttt{score} = \texttt{raw\_score}$

Default System Prompts

Each autograder uses a specialized system prompt optimized for its evaluation approach:

PerCriterionGrader - Detailed criterion-by-criterion evaluation with strict JSON formatting requirements. The prompt instructs the LLM to evaluate each criterion independently, handling both positive and negative criteria with specific response formats.

PerCriterionOneShotGrader - Streamlined prompt for evaluating all criteria in a single response. Focuses on providing verdicts (MET/UNMET) and explanations for each criterion in a structured JSON format.

RubricAsJudgeGrader - Holistic evaluation prompt that asks the LLM to consider the output as a whole and provide a single overall score from 0-100, taking into account the weights of all criteria.

You can view the complete default prompts in the source files:

• per_criterion_grader.py
• per_criterion_one_shot_grader.py
• rubric_as_judge_grader.py

Customizing System Prompts: You can override the default system prompt by passing a system_prompt parameter to any autograder:

grader = PerCriterionGrader(
    generate_fn=your_function,
    system_prompt="Your custom system prompt here"
)

XML Tag Structure: The autograders wrap content in <response> XML tags. If a query is provided (optional), it's wrapped in <query> tags. If you provide a custom system prompt, ensure it handles the response structure you're using:

<!-- Plain string response -->
<response>
{content}
</response>

<!-- Or nested with thinking/output -->
<response>
<thinking>{thinking_content}</thinking>
<output>{output_content}</output>
</response>

The structure depends on what you pass to rubric.grade(). Customize your system prompt to handle your preferred format.

Customization

You can customize grading at multiple levels:

1. Custom generate_fn (most common) Pass any typed function that returns a Pydantic model. Use any LLM provider (OpenAI, Anthropic, local models, etc.):

from rubric import PerCriterionOutput

async def your_custom_function(system_prompt: str, user_prompt: str) -> PerCriterionOutput:
    # Your LLM call here with structured outputs
    ...
    return PerCriterionOutput(criterion_status="MET", explanation="...")

grader = PerCriterionGrader(generate_fn=your_custom_function)

Each autograder requires a specific return type:

• PerCriterionGrader → PerCriterionOutput
• PerCriterionOneShotGrader → OneShotOutput
• RubricAsJudgeGrader → RubricAsJudgeOutput

2. Create custom autograder Subclass Autograder and implement the abstract methods:

• judge() - Evaluates the submission and returns raw results
• aggregate() - Transforms judge results into an EvaluationReport

The generate_fn pattern is optional - you can make LLM calls directly, use multiple functions, or skip LLMs entirely.

3. Override system prompts Customize the default prompts for built-in autograders:

grader = PerCriterionGrader(
    generate_fn=your_function,
    system_prompt="Your custom system prompt here"
)

Error Handling

Since v2.0.0, validation happens at generation time via Pydantic models. Your generate_fn is responsible for:

1. Structured outputs - Use your LLM provider's structured output features (JSON schema, function calling, etc.) to ensure valid responses
2. Retry logic - Implement retries within your generate_fn if needed
3. Validation - Return a validated Pydantic model (PerCriterionOutput, OneShotOutput, or RubricAsJudgeOutput)

If your generate_fn returns invalid data, Pydantic will raise a ValidationError.

Example with retries:

from pydantic import ValidationError
from rubric import PerCriterionOutput

async def generate_with_retries(system_prompt: str, user_prompt: str, max_retries: int = 3) -> PerCriterionOutput:
    for attempt in range(max_retries):
        try:
            response = await your_llm_call(system_prompt, user_prompt)
            return PerCriterionOutput.model_validate_json(response)
        except ValidationError as e:
            if attempt == max_retries - 1:
                raise
            continue  # Retry on validation error

Best practice: Use structured outputs (JSON schema constrained decoding) in your LLM client to avoid validation errors entirely.

Score Fields

The normalize Parameter

# Default: normalized 0-1 scores
grader = PerCriterionGrader(generate_fn=your_function)
result = await rubric.grade(text, autograder=grader)
print(result.score)      # 0.85 (normalized)
print(result.raw_score)  # 12.75 (raw weighted sum)

# Raw scores
grader = PerCriterionGrader(generate_fn=your_function, normalize=False)
result = await rubric.grade(text, autograder=grader)
print(result.score)      # 12.75 (raw, can be negative)
print(result.raw_score)  # 12.75 (same as score)

Loading Rubrics

# Direct construction
rubric = Rubric([
    Criterion(weight=10.0, requirement="States Q4 2023 base margin as 17.2%"),
    Criterion(weight=8.0, requirement="Explicitly uses Shapley attribution for decomposition"),
    Criterion(weight=-15.0, requirement="Uses total deliveries instead of cash-only deliveries")
])

# From list of dictionaries
rubric = Rubric.from_dict([
    {"weight": 10.0, "requirement": "States Q4 2023 base margin as 17.2%"},
    {"weight": 8.0, "requirement": "Explicitly uses Shapley attribution for decomposition"},
    {"weight": -15.0, "requirement": "Uses total deliveries instead of cash-only deliveries"}
])

# From JSON string
rubric = Rubric.from_json('[{"weight": 10.0, "requirement": "Example requirement"}]')

# From YAML string
yaml_data = '''
- weight: 10.0
  requirement: "Example requirement"
'''
rubric = Rubric.from_yaml(yaml_data)

# From files
rubric = Rubric.from_file('rubric.json')
rubric = Rubric.from_file('rubric.yaml')

JSON Format

[
  {
    "weight": 10.0,
    "requirement": "States Q4 2023 base margin as 17.2%"
  },
  {
    "weight": 8.0,
    "requirement": "Explicitly uses Shapley attribution for decomposition"
  },
  {
    "weight": -15.0,
    "requirement": "Uses total deliveries instead of cash-only deliveries"
  }
]

YAML Format

- weight: 10.0
  requirement: "States Q4 2023 base margin as 17.2%"
- weight: 8.0
  requirement: "Explicitly uses Shapley attribution for decomposition"
- weight: -15.0
  requirement: "Uses total deliveries instead of cash-only deliveries"

Requirements

• Python 3.10+
• An LLM API (e.g., OpenAI, Anthropic, OpenRouter) - set appropriate API keys as environment variables

License

MIT License - see LICENSE file for details.