msewell/agent-stuff Skills

Guides writing, reviewing, and modifying Arazzo workflow specifications (OpenAPI Initiative standard for multi-step API workflows). Use when creating Arazzo documents from scratch, adding steps or workflows to existing specs, reviewing Arazzo files for correctness, or generating API workflow definitions. Covers document structure, runtime expressions, success criteria, control flow, data threading, reusable components, workflow composition, AI agent integration, and validation.

Creates, reviews, and interprets C4 software architecture diagrams (System Context, Container, Component, Dynamic, Deployment). Produces Structurizr DSL or Mermaid diagram code following C4 model best practices. Use when creating architecture diagrams for a system, reviewing existing C4 diagrams for correctness and anti-patterns, generating Structurizr DSL workspaces, producing Mermaid C4 diagrams for READMEs, or using C4 diagrams as context for design decisions, code generation, risk analysis, or onboarding.

Guides designing, reviewing, and governing RESTful APIs — resource modeling, URL structure, HTTP methods, status codes, error handling (RFC 9457), pagination, versioning, security, authentication, caching, idempotency, bulk operations, async patterns, file uploads, OpenAPI documentation, API-first process, and AI-agent consumers. Use when designing new REST API endpoints, reviewing existing API designs, adopting API-first development, running API design sessions, enforcing API contracts in CI/CD, governing an API program, choosing between REST patterns (cursor vs offset pagination, PUT vs PATCH, polling vs webhooks), writing OpenAPI specs, designing for AI-agent consumers (MCP), or making API evolution and deprecation decisions.

Guides writing idiomatic, functional-style Kotlin code using built-in language features. Use when asked to write, review, or refactor Kotlin code for immutability, pure functions, sealed types, error handling, collections, coroutines, or functional architecture patterns.

Analyzes existing code and guides new type design to make invalid states unrepresentable using type system techniques such as sum types, newtypes, typestate, branded types, and parse-don't-validate. Use when reviewing code for invalid-state bugs, refactoring types to eliminate impossible states, designing domain models, or applying compile-time correctness patterns. Language-agnostic.

Generates, reviews, and fixes Mermaid sequence diagrams following syntax rules and best practices. Use when creating sequence diagrams from system descriptions, reviewing existing Mermaid sequence diagrams for correctness, fixing parse errors, or refactoring large diagrams into focused sub-diagrams. Covers participants, arrows, activations, control flow, notes, styling, and common anti-patterns.

Guides setting up, configuring, and organizing Obsidian vaults for software engineers — folder structure, plugins, templates, Git backup, Dataview queries, and AI integrations. Also creates and edits Obsidian vault files following best practices for frontmatter schemas, wikilinks, Templater syntax, Dataview code blocks, and Canvas JSON. Use when setting up a new vault, recommending plugins, creating note templates, writing Dataview queries, configuring Git sync, advising on vault organization, or generating Obsidian-compatible Markdown files.

Writes property-based tests using Kotest's kotest-property module. Identifies testable properties, designs generators, and configures PBT for Kotlin/JVM projects. Use when writing property-based tests, creating custom Arb generators, choosing property patterns (roundtrip, invariant, idempotence, oracle), debugging shrunk counterexamples, or integrating PBT into a Kotlin test suite alongside example-based tests.

Analyzes a codebase scope for coupling issues, diagnoses coupling types using the Connascence framework, and proposes a comprehensive refactoring plan with concrete code changes. Use when asked to find coupling, reduce dependencies, decouple modules, or improve modularity in a codebase.

Guides writing fast, reliable, refactoring-friendly tests using the Nullables pattern language (James Shore's 'Testing Without Mocks'). Produces narrow, sociable, state-based tests with production code that has an infrastructure 'off switch' — no mock frameworks needed. Use when writing tests, replacing mocks with Nullables, making infrastructure code testable, adding createNull() factories, implementing output tracking, wrapping external dependencies, or adopting testing-without-mocks patterns. Covers embedded stubs, configurable responses, behavior simulation, A-Frame architecture, and incremental migration from mock-based test suites.

Instructs an LLM agent when and how to use TOON (Token-Oriented Object Notation) for encoding and generating structured data. Use when injecting structured data into context, encoding tool results, preparing RAG documents, producing structured output, or advising on TOON integration.

Reviews draft tweets and provides engagement optimization recommendations with improved alternatives. Use when the user has a draft tweet or thread and wants feedback on how to maximize reach, replies, and engagement on Twitter/X. Primarily niche-agnostic with additional guidance for tech Twitter.

Creates, reviews, and iterates on Agent Skills (the open, cross-platform format for extending AI agents). Scaffolds new skill directories, writes SKILL.md files with proper frontmatter and body structure, applies progressive disclosure, reviews existing skills for anti-patterns, and guides testing workflows. Use when the user asks to create a skill, write a SKILL.md, review or improve an existing skill, or structure agent instructions.