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Castov

by castovdev

Local MCP utilities for ports, CIDR math, timestamps, IDs, secrets, hashes, JWTs, cron, time zones, and leak scanning.

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Install Castov

Pick your client, then add it in one click or paste the config.

STDIONode.js
~/Library/Application Support/Claude/claude_desktop_config.json
claude_desktop_config.json
{
  "mcpServers": {
    "castovdev-castov": {
      "command": "npx",
      "args": [
        "-y",
        "castov"
      ]
    }
  }
}

Settings → Developer → Edit Config, merge this into mcpServers, then fully quit and reopen Claude Desktop.

We couldn’t confirm it starts correctly

We ran the install command but it didn't respond within our test window — this can mean a slow first-time install rather than a real problem.

npx -y castov

Process exited before answering initialize.

This is an experimental automated check and can have false negatives — missing environment variables, a slow cold install, etc. It doesn’t necessarily mean something’s wrong. Last checked 9d ago.

Overview

castovdev/castov exposes deterministic developer utilities to AI agents through a local JSON-RPC 2.0 stdio MCP server. Its ten tools cover port and process inspection, IPv4 CIDR calculations, timestamp and identifier decoding, cron and time-zone conversion, secret generation, JWT decoding, hashing, and secret scanning. Run it with Node.js and npm, Docker, Homebrew, or an editor integration when exact operations should stay on the local machine. Claude Desktop, Cursor, and Windsurf configurations use the `castov mcp` command.

Use cases

  • Inspect which process is using a development port
  • Calculate IPv4 subnet ranges and host counts
  • Decode timestamps from distributed-system identifiers
  • Convert epochs, cron schedules, and time zones
  • Scan code and environment blocks for leaked secrets

Key features

  • Local JSON-RPC 2.0 stdio MCP server
  • Port and process inspection
  • IPv4 CIDR and timestamp utilities
  • Offline JWT, hash, and secret operations
  • Cron and IANA time-zone conversion
  • API-key and private-key leak scanning

Security & health

What it can reach and how reliably it runs — from our own checks, not the maintainer’s claims.

ActiveLast checked 2d ago

Recent health check succeeded.

Supply-chain signal

No high-severity advisories surfaced by our automated scan.

Critical 0High 0Medium 0Low 0

Scanned 11d ago via OSV.dev · castov (npm)

Adoption & maintenance

Factual signals from GitHub, npm, and our automated checks — not a rating.

GitHub stars1Stargazers on the source repository.
npm downloads1.9kPackage downloads in the last 30 days.
Last commit4d agoMost recent push to the default branch.
Install checkInconclusiveDidn't respond in our test window — often a slow first install.

How Castov works

What castovdev/castov does

castovdev/castov provides local developer utilities through the Model Context Protocol and a command-line interface. It is intended for coding agents that need exact results for operations such as checking which process owns a listening port, calculating an IPv4 subnet, converting an epoch value, or identifying the creation time embedded in a supported ID.

The package also includes offline utilities for cron schedules, IANA time-zone conversion, cryptographic material generation, JWT inspection, digest calculation, and detecting leaked secrets in code or configuration text. Processing is described as local, with no external analytics, telemetry, or cloud round trips.

How it works

The MCP entry point runs over JSON-RPC 2.0 using stdio. It supports both Content-Length framing and newline-delimited JSON stream messages. Agents invoke named tools, while the same underlying capabilities are available through the castov CLI.

The server exposes ten tools: castov_port, castov_cidr, castov_detect_id, castov_timestamp, castov_cron, castov_timezone, castov_secret, castov_jwt_decode, castov_hash, and castov_scan_secrets. Port inspection can identify listening services and process collisions; the identifier tool handles UUIDv7, ULID, Snowflake, and MongoDB ObjectId values.

Setup and configuration

Run the MCP server without a global installation using:

Terminal
npx -y castov mcp

For Claude Desktop, add a castov entry to the MCP configuration with npx as the command and -y castov mcp as its arguments. Cursor and Windsurf provide an MCP server settings interface where the command can be entered directly; Cursor also supports a project-level .cursor/mcp.json entry with the same command and arguments.

The CLI can be run with npx castov --help, installed globally with npm install -g castov, or installed through the documented Homebrew tap. A Docker image is also available and runs the command-line tool in an Alpine-based Node.js container under the non-root node user.

Tools and capabilities

  • castov_port inspects listening ports, maps protocols, and examines process collisions.
  • castov_cidr calculates IPv4 network and wildcard masks, broadcast addresses, and usable host counts.
  • castov_detect_id extracts creation timestamps from UUIDv7, ULID, Snowflake, and MongoDB ObjectId values.
  • castov_timestamp converts Unix epochs to ISO 8601, UTC, and localized representations in both directions.
  • castov_cron explains five-field cron schedules and calculates the next five runs.
  • castov_timezone converts times between IANA zones and reports DST transition warnings.
  • castov_secret generates 256-bit hexadecimal or Base64URL values, API keys, and sortable UUIDv7 secrets.
  • castov_jwt_decode decodes JWT headers and payloads and checks expiration status without network calls.
  • castov_hash computes SHA-1, SHA-256, SHA-384, SHA-512, MD5, Base64, and Base64URL encodings.
  • castov_scan_secrets checks snippets, git diffs, and .env blocks for exposed API keys and private keys.

Limitations and notes

The MCP interface is designed for local execution and exact utility operations rather than remote service access. The documented process and port command can terminate a process when invoked with its CLI --kill option, while the MCP tool list describes the agent-facing tools as read-only. Secret scanning recognizes API-key and private-key leakage patterns, so its results should be treated as an audit aid rather than a replacement for repository security controls.

Read the full README View source on GitHub

Reviews

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Frequently Asked Questions about Castov

castovdev/castov is an MCP server that connects coding agents to local developer utilities for port and process inspection, CIDR calculations, timestamp and identifier decoding, cron and time-zone conversion, secret generation, JWT decoding, hashing, and secret scanning. It communicates over JSON-RPC 2.0 stdio without cloud round trips.

Run it with `npx -y castov mcp` from an MCP client configuration. You can also install the CLI globally with `npm install -g castov`, use the documented Homebrew tap, or run the Docker image.

Add a `castov` MCP server entry that uses `npx` with the arguments `-y`, `castov`, and `mcp`. Place it in Claude Desktop's platform-specific `claude_desktop_config.json` file.

Yes, castovdev/castov works with Cursor and Windsurf through their MCP server settings. Add a command-type server using `npx -y castov mcp`; Cursor also supports the equivalent project-level `.cursor/mcp.json` configuration.

No, the documented utilities run locally without external analytics, telemetry, or cloud round trips. JWT decoding is explicitly described as offline, and the MCP tools are intended for local processing.

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