# Prompt Engineering

LLM evaluation and prompt engineering platform

Braintrust is an AI observability and evaluation platform for tracing LLM applications, building datasets, running prompt/model experiments, scoring outputs and turning production feedback into regression tests. It fits teams that need repeatable quality gates for AI releases rather than one-off prompt demos.

LLM testing and evaluation toolkit

Promptfoo is an OpenAI-owned open-source toolkit for evaluating, red-teaming and securing LLM applications. It supports config-driven prompt/model tests, CI regression gates, red-team scans, guardrails, model security workflows, MCP Proxy, code scanning and evaluations across prompts, agents and RAG pipelines.

Open-source LLMOps platform for prompt management and evaluation

Agenta is an open-source LLMOps platform that combines prompt engineering playgrounds, prompt version management, LLM evaluation, and observability in a unified interface. It supports 50+ LLM models with side-by-side prompt comparison, A/B testing, human evaluation workflows, and OpenTelemetry-native tracing. Self-hostable with 4,000+ GitHub stars.

Open standard for portable skills across AI agents

Agent Skills is the open SKILL.md folder specification for packaging reusable instructions, scripts, references, and assets that compatible AI agents load through progressive disclosure. Originally developed by Anthropic and released as an open standard, it defines the portable format itself—not an example library, marketplace, or hosted agent product.

TypeScript AI agent standard library

Standard library of AI tools and integrations for TypeScript-based agents. Works with any AI SDK and includes ready-made integrations for search, web scraping, email, and other common tool patterns. Saves developers from rebuilding common agent capabilities from scratch, providing well-tested, type-safe building blocks for rapid AI agent development.

AI-driven development workflow template

A template system that bootstraps AI-driven development workflows for your projects. Provides structured workflows, templates, and configurations for integrating AI agents into your development process. Reduces setup time by giving teams a proven starting point for organizing AI-assisted coding, task management, and quality assurance in new and existing repositories.

Official Claude Agent Skills examples, spec, and plugin marketplace for reusable agent capabilities

Anthropic Agent Skills is Anthropic's official reference repo and Claude Code plugin marketplace for reusable Skill folders. It packages example SKILL.md workflows, document skills, a Claude API skill, templates, and the Agent Skills spec so teams can turn repeatable instructions, scripts, and resources into on-demand Claude capabilities instead of copying prompts across sessions.

Curated collection of agent skills and capabilities

Awesome Agent Skills is VoltAgent's MIT-licensed list of agent skills from official teams and the community for Claude Code, Codex, Gemini CLI, and Cursor.

Curated Claude Code resources

Official Anthropic-curated list of Claude Code tips, CLAUDE.md templates, hooks, MCP servers, and community tools. Essential reference for Claude Code users looking to optimize their workflow. Covers everything from initial setup and configuration best practices to advanced patterns like custom hooks and multi-agent orchestration with the Claude Code CLI.

Type-safe LLM function builder

BAML is a domain-specific language by BoundaryML for building reliable AI workflows and agents through schema engineering. It turns prompt engineering into a structured, type-safe discipline by letting developers declaratively define function schemas, validate LLM responses, and version prompts without fragile JSON parsing or boilerplate. BAML reframes prompt engineering as schema definition, making AI workflows testable and maintainable across models.

Claude's inline code and document generation tool

Claude's built-in capability to generate and render interactive artifacts — code, documents, SVGs, React components, and HTML — directly inline within the conversation. No setup required. Turns Claude from a text-only assistant into a creative tool that can produce runnable applications, visualizations, and interactive prototypes during natural conversation.

Context engineering patterns for AI coding assistants

Context Engineering Intro is an open-source repository by Cole Medin providing structured context engineering patterns for AI coding assistants. Built around Claude Code, it includes .claude command files, PRP templates, and the WISC framework for managing AI context in coding sessions. The repo shows how to structure project context and rules so AI assistants produce reliable, architecture-aware code. With 13K+ GitHub stars, it is a go-to reference for context-first AI coding.

Community cursor rules directory

Community-maintained collection of .cursorrules files that customize Cursor IDE's AI behavior for specific frameworks, languages, and project types. Define coding conventions, preferred libraries, architectural patterns, and style guidelines that the AI follows consistently. Popular rules exist for Next.js, React, Python, TypeScript, Tailwind, and more. Hosted on cursor.directory with 1-click installation. Essential for getting consistent, project-aware AI completions in Cursor.

OpenAI's custom chatbot builder and GPT Store

Create personalized GPT assistants with custom instructions, knowledge files, and tool integrations including browsing, DALL-E, and code interpreter. Publish to the GPT Store or keep private with no coding required. Enables anyone to build specialized AI assistants for specific domains, workflows, or audiences using OpenAI's consumer-friendly builder interface.

Programming — not prompting — LLMs

Declarative framework from Stanford University for programming language models rather than prompting them. DSPy treats LLM interactions as programmable modules with input-output signatures and uses optimization algorithms to automatically compile these modules into effective prompts or fine-tuned weights, replacing brittle prompt strings with structured, modular AI software.

Modular AI prompt framework for everyday tasks

Fabric is an open-source framework that organizes AI prompts into reusable patterns for solving everyday tasks like summarizing content, explaining code, extracting insights from videos, and generating social media posts. Written in Go with support for 20+ AI providers including OpenAI, Claude, Gemini, and Ollama, it runs from the command line and can serve as a REST API. With 40,000+ GitHub stars, Fabric bridges the gap between AI capabilities and practical workflow automation.

Structured LLM outputs with validation

Instructor is the most popular Python library for extracting structured, validated data from large language models, with over 3 million monthly downloads and ports across Python, TypeScript, Go, Ruby, Elixir, and Rust. It uses Pydantic models to define output schemas and automatically handles validation, retries, and error correction when the LLM output does not match. Instructor patches existing client libraries instead of replacing them, preserving full access to the underlying API.

Structured generation for LLMs

Outlines is an open-source Python library for structured text generation that guarantees LLM outputs conform to a defined schema or format. It constrains the model's token selection at each step so only tokens leading to valid output are considered, eliminating fragile post-processing. Supports multiple-choice constraints, regex patterns, JSON Schema, and type-safe Pydantic models — helping teams extract reliable structured data from any LLM.

Toolkit for spec-driven development with AI

GitHub's official toolkit for spec-driven development. Write specifications in natural language and let AI coding agents implement them with structure, consistency, and traceability. Bridges the gap between product requirements and AI-generated code by providing a standardized format that agents can follow reliably across complex projects.