Packages

Property-based testing framework for JavaScript and TypeScript. Generates hundreds of random test cases automatically to find edge cases that example-based tests miss. Inspired by Haskell's QuickCheck. When a failure is found, fast-check automatically shrinks the input to the smallest failing case. Works with Jest, Vitest, Mocha, and any test runner. Used by companies like Docusaurus, material-ui, and fp-ts for invariant testing.

Modern high-performance Python web API framework — async-first REST API framework with automatic OpenAPI/Swagger documentation, Pydantic v2 validation, and dependency injection. FastAPI features: @app.get/post/put/delete/patch decorators, Pydantic models for request/response validation, automatic JSON serialization, OpenAPI schema generation at /docs and /redoc, Depends() for dependency injection, BackgroundTasks, OAuth2/JWT security, File/UploadFile, HTTPException, APIRouter for route organization, middleware, websockets, streaming responses, async/sync handlers, and excellent editor support via type annotations.

MCP server for book discovery and reading recommendations — a Goodreads-style tool for AI agents. Enables agents to search books, get recommendations, retrieve book metadata, query reading lists, and interact with book database information to support AI-driven reading and library management workflows.

High-performance near-optimal in-memory cache for Java — Spring Boot's default cache implementation replacing Guava Cache. Caffeine implements the Window TinyLFU eviction algorithm providing near-optimal hit rates (better than LRU/LFU). Key features: time-based expiry (expireAfterWrite, expireAfterAccess), size-based eviction, reference-based eviction (weak/soft keys/values), async loading (AsyncLoadingCache), stats collection, and Guava Cache API compatibility. Part of the Caffeine family that includes Simulator (for policy evaluation) and JCF (JSR-107/JCache implementation).

MCP server and VS Code extension enabling Claude and other LLMs to interactively debug code across any language by programmatically setting breakpoints, evaluating expressions, and stepping through execution via the Debug Adapter Protocol (DAP).

Complete solution for Node.js CLI argument parsing. Commander.js provides a declarative API for defining commands, options (--flag, -f), required/optional arguments, help text generation, and version display. The most widely-used Node.js CLI framework — used by create-react-app, vue-cli, and thousands of npm tools. Simple for basic CLIs, powerful enough for complex nested subcommand CLIs.

Express.js middleware collection that sets security-related HTTP headers. A collection of 15 smaller middlewares bundled together: Content-Security-Policy (CSP), Strict-Transport-Security (HSTS), X-Frame-Options, X-Content-Type-Options, Referrer-Policy, Permissions-Policy, Cross-Origin headers, and more. A one-line addition (app.use(helmet())) provides baseline HTTP security hardening against common web vulnerabilities. Works with Express, Fastify, and other Node.js frameworks.

Intervals.icu MCP server enabling AI agents to access Intervals.icu athletic training data — fetching workout history, analyzing training load and fitness metrics (ATL, CTL, TSS), accessing power and heart rate data, and integrating Intervals.icu's cycling and endurance sport analytics into agent-driven training analysis workflows.

MCP server for Kubit — an AI-powered product analytics platform that queries your data warehouse using natural language. Enables AI agents to query product metrics and analytics from your existing data warehouse (Snowflake, BigQuery, etc.) through Kubit's NL-to-SQL layer, without writing SQL.

Full-featured PHP web framework providing Eloquent ORM, Artisan CLI scaffolding, Blade templating, a service container for dependency injection, and first-party packages for queues, broadcasting, and authentication.

MCP server for LibreNMS — the popular open-source auto-discovering network monitoring system. Enables AI agents to query LibreNMS for device status, SNMP data, port statistics, alerts, and network topology — supporting AI-driven network operations, troubleshooting, and capacity planning workflows.

API mocking library that intercepts HTTP requests at the network level using Service Workers (browser) or native Node.js interceptors. MSW mocks work identically in browser and Node.js without changing application code — no dependency injection or adapter patterns needed. Define request handlers once, use them in development (browser), integration tests (Node.js/Vitest/Jest), and E2E tests (Playwright/Cypress). Considered the gold standard for frontend API mocking.

Developer-focused email sending API with powerful routing, parsing, and validation features for transactional email delivery.

HTML and XML parsing library for Ruby — the standard Ruby library for parsing, querying, and modifying HTML/XML documents. Nokogiri wraps libxml2 and libgumbo (HTML5 parser) for fast, standards-compliant parsing. Key APIs: Nokogiri::HTML5(html_string) for HTML5 parsing, Nokogiri::XML(xml_string) for XML, CSS selectors (doc.css('div.agent-card')), XPath (doc.xpath('//agent[@status="active"]')), text extraction (.text), attribute access (.attr('href')), and document modification. Used for web scraping agent tools, parsing HTML email content, processing RSS/Atom feeds, extracting agent knowledge from web pages, and XML API response handling.

MCP server for OpenCTI — an open-source threat intelligence platform for storing, analyzing, and sharing cyber threat intelligence. Enables AI agents to query threat indicators, retrieve threat actor profiles, search IOCs (Indicators of Compromise), and interact with OpenCTI's knowledge graph for AI-assisted threat analysis and SOC workflows.

AWS-maintained Apache 2.0 fork of Elasticsearch 7.10 providing distributed full-text search, vector/kNN search, and analytics via a REST API compatible with Elasticsearch tooling.

Perplexity AI MCP server enabling AI agents to access Perplexity's AI-powered search — querying Perplexity Sonar API for real-time web search with citations, getting AI-synthesized answers with source references, and integrating Perplexity's search-augmented LLM into agent-driven research and fact-checking workflows.

MCP server for Polarion ALM — Siemens' Application Lifecycle Management platform used in automotive, aerospace, and safety-critical industries. Enables AI agents to query work items, manage requirements, access test management data, and interact with Polarion's ALM workflows — supporting AI-assisted requirements engineering and compliance documentation.

Performant, flexible React form library using uncontrolled components and ref-based state. React Hook Form (RHF) avoids re-rendering on every keystroke by using the DOM's native uncontrolled inputs rather than React state, making it significantly faster than Formik for large forms. Integrates natively with Zod, Valibot, ArkType, and Yup via @hookform/resolvers for schema validation. The standard form library for modern React applications.

Swift linting and style enforcement tool — enforces Swift style guide rules, catches common bugs, and maintains code quality. SwiftLint runs as Xcode build phase script or CLI. Configuration via .swiftlint.yml: disabled_rules, opt_in_rules, included/excluded paths, rule-specific configuration (line_length: 120). Rules: style (trailing_whitespace, colon, opening_brace), idiomatic (force_cast, force_try, implicitly_unwrapped_optional), metrics (function_body_length, file_length), lint (unused_import, unused_closure_parameter). Xcode integration shows warnings/errors inline. Supports SwiftFormat integration and custom regex rules. Essential for consistent agent iOS codebase.