Castov

Castov is a developer platform offering web tools, a command-line interface, and a Model Context Protocol (MCP) server. The page states that its utilities run locally in the browser, terminal, and AI agents, with zero-data logging and offline operation. Listed capabilities include timestamp and date inspection, time zone conversion, JSON to TypeScript, JSON formatting and validation, JWT decoding, UUID and hash generation, Base64 encoding and decoding, cron expression generation, and a diff checker. The site also describes encrypted URL shares, end-to-end encrypted cloud sync and team vaults via GitHub OAuth, Docker distribution, and several experimental Lab tools such as a Service Worker API Mocker and a P2P Ghost Tunnel. The FAQ states all tools are free with no account and no usage limits, while noting that some collaboration, cloud, and external API features may require an account or additional configuration. Some features use the network by design, including Env Vault uploads of encrypted copies and WebRTC signaling for the Developer Canvas.

Key features

• 100% client-side tool execution in the browser with zero-data logging as described on the page
• Works offline
• Web, CLI (castov), and MCP server (castov mcp) for Cursor and Claude
• Unix timestamp converter with seconds and milliseconds detection
• Time zone converter and world clock using IANA time zones with daylight saving rules
• JSON to TypeScript conversion
• JSON formatter and validator
• JWT decoder
• UUID generator
• Hash generator
• Base64 encode and decode
• Cron expression generator
• Diff checker
• Encrypted URL shares using the URL hash fragment
• End-to-end encrypted cloud sync and team vaults via GitHub OAuth
• Docker image castovdev/castov:latest for running the CLI and MCP runtime
• Service Worker API Mocker (Lab experiment)
• Tool pipelines for passing output between utilities

Best suited for

• Developers working with Unix timestamps and time zones
• Developers converting JSON to TypeScript interfaces
• Teams sharing .env files through encrypted team vaults
• Developers using Cursor or Claude who want an MCP server for developer utilities
• CI/CD and terminal workflows using the CLI or Docker container

Pricing

Free according to the website FAQ: all tools are free, with no account and no usage limits. The site states ads may be shown in the future.