buildEvaluationInstructions method

@override List<ChatMessage>? buildEvaluationInstructions(List<ChatMessage> messages, ChatResponse modelResponse, List<EvaluationContext> additionalContext)

Builds the evaluation instructions (system + user messages).

Return null to signal that a required context was missing.

Implementation

@override
List<ChatMessage>? buildEvaluationInstructions(
  List<ChatMessage> messages,
  ChatResponse modelResponse,
  List<EvaluationContext> additionalContext,
) {
  final userRequest = messages.lastUserMessage?.text ?? '';
  final response = modelResponse.text;
  final prompt = '''
# Definition
**Coherence** refers to the logical and orderly presentation of ideas in a response, allowing the reader to easily follow and understand the writer's train of thought. A coherent answer directly addresses the question with clear connections between sentences and paragraphs, using appropriate transitions and a logical sequence of ideas.

# Ratings
## [Coherence: 1] (Incoherent Response)
**Definition:** The response lacks coherence entirely. Disjointed words or phrases with no logical connection to the question.

## [Coherence: 2] (Poorly Coherent Response)
**Definition:** Minimal coherence with fragmented sentences and limited connection to the question.

## [Coherence: 3] (Partially Coherent Response)
**Definition:** Partially addresses the question but exhibits issues in logical flow and organization.

## [Coherence: 4] (Coherent Response)
**Definition:** Coherent and effectively addresses the question with logically organized ideas and clear connections.

## [Coherence: 5] (Highly Coherent Response)
**Definition:** Exceptionally coherent, demonstrating sophisticated organization and seamless flow.

# Data
QUERY: $userRequest
RESPONSE: $response

# Tasks
## Please provide your assessment Score for the previous RESPONSE in relation to the QUERY based on the Definitions above.
- **ThoughtChain**: Think step by step. Start with "Let's think step by step:".
- **Explanation**: A very short explanation of why you think the input Data should get that Score.
- **Score**: An integer score (1–5) based on the definitions.

## Please provide your answers between the tags: <S0>your chain of thoughts</S0>, <S1>your explanation</S1>, <S2>your Score</S2>.
# Output
''';
  return [
    ChatMessage.fromText(ChatRole.system, _systemPrompt),
    ChatMessage.fromText(ChatRole.user, prompt),
  ];
}