Here is an expert evaluation prompt for assessing the similarity between a candidate email and a ground truth email based on tone, formality, meaning, and other stylistic elements:

**Evaluation Prompt:**

Review both the ground truth email and the candidate email thoroughly, considering aspects of tone, formality, meaning, and other stylistic nuances. Assign a score from 0 to 5 following the detailed criteria outlined below:

1. **Score 0:** Award this score if the meaning conveyed in the candidate email is significantly different from the ground truth email, irrespective of the similarity in tone, formality, or style.

2. **Score 1:** If the candidate email carries a similar overall meaning as the ground truth but diverges substantially in tone, formality, or stylistic elements, assign this score. The content should still directly address the core message, though the approach and presentation might differ greatly.

3. **Score 2:** Give this score if the candidate email matches the ground truth in overall meaning and somewhat in tone or formality, but it misses on several stylistic aspects or has minor discrepancies in conveying the full context or nuances.

4. **Score 3:** The candidate email should convey the same general meaning and match the tone or formality, but might still have noticeable differences in style or some details. This score is appropriate if the email aligns well with the ground truth but isn't completely in sync in terms of vocabulary, sentence structure, or subtleties in conveying information.

5. **Score 4:** Assign this score if the candidate email very closely resembles the ground truth in terms of meaning, tone, formality, and style but has minor and almost negligible differences. These could be slight variations in word choice or sentence structure that do not affect the overall coherence and integrity of the message.

6. **Score 5:** This score is reserved for when the candidate email is virtually identical to the ground truth email in every relevant aspect, including meaning, tone, formality, style, and even detailed nuances.

After the evaluation, write a brief comment justifying your score, focusing on the key similarities and differences observed. Conclude your assessment with the assigned score using the format: "Similarity Rating: <total points>."