Prompt 约束技巧
如何通过 Prompt 有效约束大模型行为
核心原理
大模型的行为模式
大模型本质: 概率预测下一个 token
输入: "Rc cannot be sent"
模型思考: P("用 Arc") > P("分析领域约束后...")
默认行为: 选择概率最高的路径 (通常是最短、最常见的回答)
问题: 最高概率 ≠ 最佳答案
约束的作用
约束 = 改变概率分布
无约束: P("用 Arc") = 0.7, P("分析后回答") = 0.3
有约束: P("用 Arc") = 0.2, P("分析后回答") = 0.8
约束词提高了"遵循指令"路径的概率
约束词层级
强度等级
| 等级 | 约束词 | 效果 | 使用场景 |
|---|---|---|---|
| L5 最强 | CRITICAL, MUST, NEVER, MANDATORY | 几乎 100% 遵循 | 核心规则，不可违反 |
| L4 强 | IMPORTANT, REQUIRED, ALWAYS | 90%+ 遵循 | 重要规则 |
| L3 中 | should, recommended, prefer | 70%+ 遵循 | 建议性规则 |
| L2 弱 | can, may, consider | 50% 遵循 | 可选项 |
| L1 最弱 | optionally, if needed | 30% 遵循 | 边缘情况 |
使用示例
# L5: 核心规则
CRITICAL: You MUST load both L1 and L3 skills.
NEVER skip the domain constraint analysis.
This is MANDATORY and NON-NEGOTIABLE.
# L4: 重要规则
IMPORTANT: Always include the reasoning chain.
You are REQUIRED to reference domain rules.
# L3: 建议
You should trace through all layers.
It is recommended to provide code examples.
# L2: 可选
You can include additional context.
You may reference related skills.
# L1: 边缘
Optionally, mention performance implications.
有效约束模式
1. CRITICAL + MUST 组合
CRITICAL: You MUST follow the meta-cognition framework.
效果:
- CRITICAL 提升注意力
- MUST 强制执行
- 组合使用 > 单独使用
2. 正反对比
DO:
- Load both L1 and L3 skills
- Output reasoning chain
- Reference domain constraints
DON'T:
- Skip domain analysis
- Output only "use Arc"
- Ignore the context
效果: 明确边界，减少歧义
3. 示例对比
CORRECT Response:
Reasoning Chain
+-- Layer 1: Send/Sync Error +-- Layer 3: Web Domain constraint +-- Layer 2: Design decision
WRONG Response:
Use Arc instead of Rc.
效果: 具体示例 > 抽象描述
4. 条件约束
**IF** domain keywords are present,
**THEN** you MUST load BOTH L1 and L3 skills.
**IF** error code detected,
**THEN** start from Layer 1 and trace UP.
效果: 清晰的触发条件
5. 步骤强制
## STEP 1: IDENTIFY (MANDATORY)
...
## STEP 2: LOAD SKILLS (MANDATORY)
...
## STEP 3: OUTPUT (MANDATORY)
...
效果: 步骤编号 + MANDATORY 确保顺序执行
格式化增强
大写强调
# 效果递增
should do this → 弱
SHOULD do this → 中
You SHOULD do this → 中强
You MUST do this → 强
CRITICAL: You MUST... → 最强
结构化布局
# 好 - 清晰的视觉层级
## STEP 1: IDENTIFY LAYER
### Layer 1 Signals:
- Error codes: E0382, E0597
- Keywords: borrow, lifetime
### Layer 3 Signals:
- Domain keywords: Web API, HTTP
---
# 差 - 无结构
First identify the layer. Look for error codes like E0382
or keywords like borrow. Also check for domain keywords...
表格约束
# 好 - 表格清晰
| Keywords | Action |
|----------|--------|
| Web API, HTTP | Load domain-web |
| payment | Load domain-fintech |
# 差 - 文字描述
If you see Web API or HTTP, load domain-web.
If you see payment, load domain-fintech.
常用约束词汇表
强制执行类
| 词 | 含义 | 示例 |
|---|---|---|
MUST | 必须 | You MUST include... |
NEVER | 绝不 | NEVER skip... |
ALWAYS | 总是 | ALWAYS check... |
REQUIRED | 必需 | This is REQUIRED |
MANDATORY | 强制 | MANDATORY step |
NON-NEGOTIABLE | 不可商量 | This is NON-NEGOTIABLE |
禁止类
| 词 | 含义 | 示例 |
|---|---|---|
NEVER | 绝不 | NEVER output only... |
DO NOT | 不要 | DO NOT skip... |
AVOID | 避免 | AVOID generic answers |
FORBIDDEN | 禁止 | This is FORBIDDEN |
NOT ACCEPTABLE | 不可接受 | Partial compliance is NOT ACCEPTABLE |
条件类
| 词 | 含义 | 示例 |
|---|---|---|
IF...THEN | 如果...则 | IF domain detected, THEN load... |
WHEN | 当 | WHEN error code present... |
UNLESS | 除非 | UNLESS explicitly asked... |
ONLY IF | 仅当 | ONLY IF user requests... |
强调类
| 词 | 含义 | 示例 |
|---|---|---|
CRITICAL | 关键 | CRITICAL: This is essential |
IMPORTANT | 重要 | IMPORTANT: Note that... |
NOTE | 注意 | NOTE: This affects... |
WARNING | 警告 | WARNING: Do not... |
rust-skills 中的实践
Hook 脚本约束
=== MANDATORY: META-COGNITION ROUTING ===
CRITICAL: You MUST follow the COMPLETE meta-cognition framework.
Partial compliance (only loading L1 skill) is NOT ACCEPTABLE.
# 使用技巧:
# 1. 标题用 === 包围，视觉突出
# 2. CRITICAL + MUST 组合
# 3. 明确说明什么是不可接受的
Skill Description 约束
description: "CRITICAL: Use for ALL Rust questions. Triggers on: ..."
# 使用技巧:
# 1. 以 CRITICAL 开头
# 2. 明确触发条件
# 3. 关键词用 Triggers on: 标记
输出格式约束
## STEP 3: MANDATORY OUTPUT FORMAT
Your response MUST include ALL of these sections:
### Reasoning Chain
+-- Layer 1: [specific error] | ^ +-- Layer 3: [domain constraint] | v +-- Layer 2: [design decision]
# 使用技巧:
# 1. MANDATORY + ALL 双重强调
# 2. 提供精确模板
# 3. 用代码块展示格式
正反对比约束
CORRECT Response:
Reasoning Chain
+-- Layer 1: Send/Sync Error ...
WRONG Response (stops at L1):
Problem: Rc is not Send Solution: Use Arc
# 使用技巧:
# 1. 并列展示正确/错误
# 2. 标注 (stops at L1) 说明错在哪
# 3. 让模型清楚知道什么是不想要的
常见错误
1. 约束太弱
# 差
You should probably include the reasoning chain.
It would be nice to reference domain constraints.
# 好
You MUST include the reasoning chain.
CRITICAL: Reference domain constraints.
2. 约束太模糊
# 差
Follow the meta-cognition framework.
# 好
STEP 1: Identify entry layer (L1/L2/L3)
STEP 2: Load appropriate skills using Skill() tool
STEP 3: Trace through layers (UP or DOWN)
STEP 4: Output with reasoning chain format
3. 没有示例
# 差
Output should include reasoning chain.
# 好
Output MUST include reasoning chain:
Reasoning Chain
+-- Layer 1: [error] +-- Layer 3: [constraint] +-- Layer 2: [decision]
4. 没有反例
# 差
Include domain analysis.
# 好
Include domain analysis.
WRONG (without domain analysis):
"Use Arc instead of Rc"
CORRECT (with domain analysis):
"From domain-web: handlers run on any thread,
therefore Arc + State extractor is recommended"
约束效果验证
测试方法
1. 准备测试问题
"Web API 报错 Rc cannot be sent"
2. 无约束测试
→ 观察默认输出
3. 加约束测试
→ 观察是否遵循
4. 调整约束强度
→ 找到最小有效约束
检查清单
□ 是否加载了指定的 Skills?
□ 是否执行了领域检测?
□ 是否输出了推理链?
□ 是否引用了领域约束?
□ 是否遵循了输出格式?
最佳实践总结
1. 约束强度选择
| 情况 | 推荐强度 |
|---|---|
| 核心流程 | CRITICAL + MUST |
| 重要规则 | IMPORTANT / REQUIRED |
| 建议性 | should / recommended |
| 可选项 | can / may |
2. 约束结构
1. 先声明约束级别 (CRITICAL/IMPORTANT)
2. 再描述具体要求 (You MUST...)
3. 提供正确示例 (CORRECT:)
4. 提供反面示例 (WRONG:)
5. 条件触发 (IF...THEN...)
3. 格式化
✓ 使用大写强调关键词
✓ 使用表格组织规则
✓ 使用编号步骤
✓ 使用代码块展示格式
✓ 使用分隔线划分区域
4. 迭代优化
观察输出 → 识别偏差 → 增强约束 → 再次测试
常见调整:
- 约束词不够强 → 升级到 CRITICAL/MUST
- 规则不够具体 → 添加示例
- 遗漏情况 → 添加条件分支
一句话总结
约束的本质是改变模型的概率分布，让"遵循指令"的路径概率高于"默认行为"的路径。
关键技巧:
- 强度递增: should < IMPORTANT < CRITICAL + MUST
- 正反对比: CORRECT vs WRONG 示例
- 格式模板: 具体格式 > 抽象描述
- 条件触发: IF...THEN 明确边界