我用 7 版 Prompt 把合同抽取准确率从 71% 提到 94%，Token 反而降了 38%

import json
from openai import OpenAI
import tiktoken

client = OpenAI(api_key="sk-xxx")
enc = tiktoken.encoding_for_model("gpt-4o-mini")

def count_tokens(text: str) -> int:
    return len(enc.encode(text))

def extract_v1(contract: str) -> dict:
    prompt = f"""请从下面的合同中抽取 party_a, party_b, sign_date,
amount, payment_terms, penalty_rate 六个字段。

合同：
{contract}
"""
    resp = client.chat.completions.create(
        model="gpt-4o-mini",
        messages=[{"role": "user", "content": prompt}],
        temperature=0,
        max_tokens=512,
    )
    return resp.choices[0].message.content

SCHEMA = {
    "type": "object",
    "properties": {
        "party_a": {"type": "string"},
        "party_b": {"type": "string"},
        "sign_date": {"type": "string", "description": "YYYY-MM-DD，签署日"},
        "amount": {"type": "number", "description": "含税总价，单位元"},
        "payment_terms": {
            "type": "array",
            "items": {"type": "string"},
            "description": "付款节点，如 '30%预付'"
        },
        "penalty_rate": {"type": "number", "description": "日违约金比例，如 0.0005"}
    },
    "required": ["party_a", "party_b", "sign_date", "amount"]
}

def extract_v5(contract: str) -> dict:
    system = (
        "你是合同信息抽取引擎。只输出 JSON，不要 markdown，不要解释。"
        f"必须符合以下 JSON Schema：\n{json.dumps(SCHEMA, ensure_ascii=False)}"
    )
    resp = client.chat.completions.create(
        model="gpt-4o-mini",
        messages=[
            {"role": "system", "content": system},
            {"role": "user", "content": contract},
        ],
        temperature=0,
        max_tokens=512,
        response_format={"type": "json_object"},
    )
    return json.loads(resp.choices[0].message.content)

SYSTEM_V7 = """你是合同抽取引擎，只输出 JSON。
字段定义：
- party_a/party_b: 甲乙方全称
- sign_date: 签署日，YYYY-MM-DD
- amount: 含税总价，数字，单位元
- payment_terms: 字符串数组
- penalty_rate: 日违约金比例，小数
输出后自查：金额是否含税、日期是否为签署日。
若不一致，直接给修正后的最终结果，不要输出过程。"""

def extract_v7(contract: str, retry: int = 2) -> dict:
    for _ in range(retry):
        try:
            resp = client.chat.completions.create(
                model="gpt-4o-mini",
                messages=[
                    {"role": "system", "content": SYSTEM_V7},
                    {"role": "user", "content": contract},
                ],
                temperature=0,
                max_tokens=512,
                response_format={"type": "json_object"},
            )
            return json.loads(resp.choices[0].message.content)
        except json.JSONDecodeError:
            continue
    raise RuntimeError("抽取失败")