Agent Skills: Prompt Engineering — Operational Skill

Prompt Engineering — Operational Skill

Modern Best Practices (January 2026): versioned prompts, explicit output contracts, regression tests, and safety threat modeling for tool/RAG prompts (OWASP LLM Top 10: https://owasp.org/www-project-top-10-for-large-language-model-applications/).

This skill provides operational guidance for building production-ready prompts across standard tasks, RAG workflows, agent orchestration, structured outputs, hidden reasoning, and multi-step planning.

All content is operational, not theoretical. Focus on patterns, checklists, and copy-paste templates.

Quick Start (60 seconds)

1. Pick a pattern from the decision tree (structured output, extractor, RAG, tools/agent, rewrite, classification).
2. Start from a template in assets/ and fill in TASK, INPUT, RULES, and OUTPUT FORMAT.
3. Add guardrails: instruction/data separation, “no invented details”, missing → null/explicit missing.
4. Add validation: JSON parse check, schema check, citations check, post-tool checks.
5. Add evals: 10–20 cases while iterating, 50–200 before release, plus adversarial injection cases.

Model Notes (2026)

This skill includes Claude Code + Codex CLI optimizations:

• Action directives: Frame for implementation, not suggestions
• Parallel tool execution: Independent tool calls can run simultaneously
• Long-horizon task management: State tracking, incremental progress, context compaction resilience
• Positive framing: Describe desired behavior rather than prohibitions
• Style matching: Prompt formatting influences output style
• Domain-specific patterns: Specialized guidance for frontend, research, and agentic coding
• Style-adversarial resilience: Stress-test refusals with poetic/role-play rewrites; normalize or decline stylized harmful asks before tool use

Prefer “brief justification” over requesting chain-of-thought. When using private reasoning patterns, instruct: think internally; output only the final answer.

Quick Reference

| Task | Pattern to Use | Key Components | When to Use | |------|----------------|----------------|-------------| | Machine-parseable output | Structured Output | JSON schema, "JSON-only" directive, no prose | API integrations, data extraction | | Field extraction | Deterministic Extractor | Exact schema, missing->null, no transformations | Form data, invoice parsing | | Use retrieved context | RAG Workflow | Context relevance check, chunk citations, explicit missing info | Knowledge bases, documentation search | | Internal reasoning | Hidden Chain-of-Thought | Internal reasoning, final answer only | Classification, complex decisions | | Tool-using agent | Tool/Agent Planner | Plan-then-act, one tool per turn | Multi-step workflows, API calls | | Text transformation | Rewrite + Constrain | Style rules, meaning preservation, format spec | Content adaptation, summarization | | Classification | Decision Tree | Ordered branches, mutually exclusive, JSON result | Routing, categorization, triage |

Decision Tree: Choosing the Right Pattern

User needs: [Prompt Type]
  |-- Output must be machine-readable?
  |     |-- Extract specific fields only? -> **Deterministic Extractor Pattern**
  |     `-- Generate structured data? -> **Structured Output Pattern (JSON)**
  |
  |-- Use external knowledge?
  |     `-- Retrieved context must be cited? -> **RAG Workflow Pattern**
  |
  |-- Requires reasoning but hide process?
  |     `-- Classification or decision task? -> **Hidden Chain-of-Thought Pattern**
  |
  |-- Needs to call external tools/APIs?
  |     `-- Multi-step workflow? -> **Tool/Agent Planner Pattern**
  |
  |-- Transform existing text?
  |     `-- Style/format constraints? -> **Rewrite + Constrain Pattern**
  |
  `-- Classify or route to categories?
        `-- Mutually exclusive rules? -> **Decision Tree Pattern**

Copy/Paste: Minimal Prompt Skeletons

1) Generic "output contract" skeleton

TASK:
{{one_sentence_task}}

INPUT:
{{input_data}}

RULES:
- Follow TASK exactly.
- Use only INPUT (and tool outputs if tools are allowed).
- No invented details. Missing required info -> say what is missing.
- Keep reasoning hidden.
- Follow OUTPUT FORMAT exactly.

OUTPUT FORMAT:
{{schema_or_format_spec}}

2) Tool/agent skeleton (deterministic)

AVAILABLE TOOLS:
{{tool_signatures_or_names}}

WORKFLOW:
- Make a short plan.
- Call tools only when required to complete the task.
- Validate tool outputs before using them.
- If the environment supports parallel tool calls, run independent calls in parallel.

3) RAG skeleton (grounded)

RETRIEVED CONTEXT:
{{chunks_with_ids}}

RULES:
- Use only retrieved context for factual claims.
- Cite chunk ids for each claim.
- If evidence is missing, say what is missing.

Operational Checklists

Use these references when validating or debugging prompts:

• frameworks/shared-skills/skills/ai-prompt-engineering/references/quality-checklists.md
• frameworks/shared-skills/skills/ai-prompt-engineering/references/production-guidelines.md

Context Engineering (2026)

True expertise in prompting extends beyond writing instructions to shaping the entire context in which the model operates. Context engineering encompasses:

• Conversation history: What prior turns inform the current response
• Retrieved context (RAG): External knowledge injected into the prompt
• Structured inputs: JSON schemas, system/user message separation
• Tool outputs: Results from previous tool calls that shape next steps

Context Engineering vs Prompt Engineering

| Aspect | Prompt Engineering | Context Engineering | |--------|-------------------|---------------------| | Focus | Instruction text | Full input pipeline | | Scope | Single prompt | RAG + history + tools | | Optimization | Word choice, structure | Information architecture | | Goal | Clear instructions | Optimal context window |

Key Context Engineering Patterns

1. Context Prioritization: Place most relevant information first; models attend more strongly to early context.

2. Context Compression: Summarize history, truncate tool outputs, select most relevant RAG chunks.

3. Context Separation: Use clear delimiters (<system>, <user>, <context>) to separate instruction types.

4. Dynamic Context: Adjust context based on task complexity - simple tasks need less context, complex tasks need more.

Core Concepts vs Implementation Practices

Core Concepts (Vendor-Agnostic)

• Prompt contract: inputs, allowed tools, output schema, max tokens, and refusal rules.
• Context engineering: conversation history, RAG context, tool outputs, and structured inputs shape model behavior.
• Determinism controls: temperature/top_p, constrained decoding/structured outputs, and strict formatting.
• Cost & latency budgets: prompt length and max output drive tokens and tail latency; enforce hard limits and measure p95/p99.
• Evaluation: golden sets + regression gates + A/B + post-deploy monitoring.
• Security: prompt injection, data exfiltration, and tool misuse are primary threats (OWASP LLM Top 10: https://owasp.org/www-project-top-10-for-large-language-model-applications/).

Implementation Practices (Model/Platform-Specific)

• Use model-specific structured output features when available; keep a schema validator as the source of truth.
• Align tracing/metrics with OpenTelemetry GenAI semantic conventions (https://opentelemetry.io/docs/specs/semconv/gen-ai/).

Do / Avoid

Do

• Do keep prompts small and modular; centralize shared fragments (policies, schemas, style).
• Do add a prompt eval harness and block merges on regressions.
• Do prefer "brief justification" over requesting chain-of-thought; treat hidden reasoning as model-internal.

Avoid

• Avoid prompt sprawl (many near-duplicates with no owner or tests).
• Avoid brittle multi-step chains without intermediate validation.
• Avoid mixing policy and product copy in the same prompt (harder to audit and update).

Navigation: Core Patterns

• Core Patterns - 7 production-grade prompt patterns
  • Structured Output (JSON), Deterministic Extractor, RAG Workflow
  • Hidden Chain-of-Thought, Tool/Agent Planner, Rewrite + Constrain, Decision Tree
  • Each pattern includes structure template and validation checklist

Navigation: Best Practices

• Best Practices (Core) - Foundation rules for production-grade prompts

  • System instruction design, output contract specification, action directives
  • Context handling, error recovery, positive framing, style matching, style-adversarial red teaming
  • Anti-patterns, Claude 4+ specific optimizations

• Production Guidelines - Deployment and operational guidance

  • Evaluation & testing (Prompt CI/CD), model parameters, few-shot selection
  • Safety & guardrails, conversation memory, context compaction resilience
  • Answer engineering, decomposition, multilingual/multimodal, benchmarking
  • CI/CD Tools (2026): Promptfoo, DeepEval integration patterns
  • Security (2026): PromptGuard 4-layer defense, Microsoft Prompt Shields, taint tracking

• Quality Checklists - Validation checklists before deployment

  • Prompt QA, JSON validation, agent workflow checks
  • RAG workflow, safety & security, performance optimization
  • Testing coverage, anti-patterns, quality score rubric

• Domain-Specific Patterns - Claude 4+ optimized patterns for specialized domains

  • Frontend/visual code: Creativity encouragement, design variations, micro-interactions
  • Research tasks: Success criteria, verification, hypothesis tracking
  • Agentic coding: No speculation rule, principled implementation, investigation patterns
  • Cross-domain best practices and quality modifiers

Navigation: Specialized Patterns

• RAG Patterns - Retrieval-augmented generation workflows

  • Context grounding, chunk citation, missing information handling

• Agent and Tool Patterns - Tool use and agent orchestration

  • Plan-then-act workflows, tool calling, multi-step reasoning, generate-verify-revise chains
  • Multi-Agent Orchestration (2026): centralized, handoff, federated patterns; plan-and-execute (90% cost reduction)

• Extraction Patterns - Deterministic field extraction

  • Schema-based extraction, null handling, no hallucinations

• Reasoning Patterns (Hidden CoT) - Internal reasoning without visible output

  • Hidden reasoning, final answer only, classification workflows
  • Extended Thinking API (Claude 4+): budget management, think tool, multishot patterns

• Additional Patterns - Extended prompt engineering techniques

  • Advanced patterns, edge cases, optimization strategies

• Prompt Testing & CI/CD - Automated prompt evaluation pipelines

  • Promptfoo, DeepEval integration, regression detection, A/B testing, quality gates

• Multimodal Prompt Patterns - Vision, audio, and document input patterns

  • Image description, OCR+LLM, bounding box prompts, Whisper conditioning, video frame analysis

• Prompt Security & Defense - Securing LLM applications against adversarial attacks

  • Injection detection (PromptGuard, Prompt Shields), defense-in-depth, taint tracking, red team testing

Navigation: Templates

Templates are copy-paste ready and organized by complexity:

Quick Templates

• Quick Template - Fast, minimal prompt structure

Standard Templates

• Standard Template - Production-grade operational prompt
• Agent Template - Tool-using agent with planning
• RAG Template - Retrieval-augmented generation
• Chain-of-Thought Template - Hidden reasoning pattern
• JSON Extractor Template - Deterministic field extraction
• Prompt Evaluation Template - Regression tests, A/B testing, rollout gates

External Resources

External references are listed in data/sources.json:

• Official documentation (OpenAI, Anthropic, Google)
• LLM frameworks (LangChain, LlamaIndex)
• Vector databases (Pinecone, Weaviate, FAISS)
• Evaluation tools (OpenAI Evals, HELM)
• Safety guides and standards
• RAG and retrieval resources

Freshness Rule (2026)

When asked for “latest” prompting recommendations, prefer provider docs and standards from data/sources.json. If web search is unavailable, state the constraint and avoid overconfident “current best” claims.

Related Skills

This skill provides foundational prompt engineering patterns. For specialized implementations:

AI/LLM Skills:

• AI Agents Development - Production agent patterns, MCP integration, orchestration
• AI LLM Engineering - LLM application architecture and deployment
• AI LLM RAG Engineering - Advanced RAG pipelines and chunking strategies
• AI LLM Search & Retrieval - Search optimization, hybrid retrieval, reranking
• AI LLM Development - Fine-tuning, evaluation, dataset creation

Software Development Skills:

• Software Architecture Design - System design patterns
• Software Backend - Backend implementation
• Foundation API Design - API design and contracts

Usage Notes

For Claude Code:

• Reference this skill when building prompts for agents, commands, or integrations
• Use Quick Reference table for fast pattern lookup
• Follow Decision Tree to select appropriate pattern
• Validate outputs with Quality Checklists before deployment
• Use templates as starting points, customize for specific use cases

For Codex CLI:

• Use the same patterns and templates; adapt tool-use wording to the local tool interface
• For long-horizon tasks, track progress explicitly (a step list/plan) and update it as work completes
• Run independent reads/searches in parallel when the environment supports it; keep writes/edits serialized
• AGENTS.md Integration: Place project-specific prompt guidance in AGENTS.md files at global (~/.codex/AGENTS.md), project-level (./AGENTS.md), or subdirectory scope for layered instructions
• Reasoning Effort: Use medium for interactive coding (default), high/xhigh for complex autonomous multi-hour tasks

Fact-Checking

• Use web search/web fetch to verify current external facts, versions, pricing, deadlines, regulations, or platform behavior before final answers.
• Prefer primary sources; report source links and dates for volatile information.
• If web access is unavailable, state the limitation and mark guidance as unverified.