Add Local Developer Utilities to Any MCP Assistant with DevUtils

AI assistants are useful at translating intent into actions, but small developer utilities are an easy place for an agent to guess. A guessed hash, a malformed JSON transformation, or a misunderstood JWT timestamp can waste more time than the original task.

DevUtils MCP Server provides a local set of 36 developer utilities through the Model Context Protocol (MCP). The server exposes hashing, encoding, ID generation, JWT inspection, JSON formatting, network calculations, and text utilities over standard input and output. The operations run locally and the project documents no external API dependency.

This tutorial installs the stable v1.1.0 release, connects it to an MCP client, verifies the transport with a real initialize request, and explains where the tool is useful and where it is not.

TL;DR

Run the server with Node.js 18 or newer:

npx -y devutils-mcp-server@1.1.0

Then add the same command to your MCP client configuration:

{
  "mcpServers": {
    "devutils": {
      "command": "npx",
      "args": ["-y", "devutils-mcp-server@1.1.0"]
    }
  }
}

After restarting the client, it can call tools such as hash_sha256, json_validate, generate_uuid, cidr_calculate, and text_stats.

Prerequisites

You need:

• Node.js 18 or newer. The project recommends Node.js 22 for its current development environment.
• An MCP-compatible client such as Claude Desktop, Cursor, VS Code Copilot, or Windsurf.
• Network access only for the first npx package download. The server itself uses stdio and is documented as having no external API dependency.

The commands below target the published v1.1.0 release. The repository default branch currently contains 1.1.1, so pinning the package version makes this walkthrough reproducible against the stable release that was checked.

Install and connect the server

The simplest path does not install a global package. npx downloads the requested package version and starts its executable:

npx -y devutils-mcp-server@1.1.0

An MCP server using stdio is not a traditional web service. It waits for JSON-RPC messages on standard input and writes protocol responses to standard output. That is why the client configuration names a command and arguments rather than a URL.

For Claude Desktop on Windows, the documented configuration file is %APPDATA%\\Claude\\claude_desktop_config.json. For a workspace-specific VS Code setup, use .vscode/mcp.json with the VS Code servers shape:

{
  "servers": {
    "devutils": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "devutils-mcp-server@1.1.0"]
    }
  }
}

Use the configuration shape required by your client. Claude Desktop, Cursor, and Windsurf use an mcpServers object in the project documentation, while VS Code uses servers and includes type: "stdio".

Verify the transport before using tools

You can verify the minimal path without opening a client. Send an MCP initialize request to the package:

echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"smoke-test","version":"1.0.0"}}}' | npx -y devutils-mcp-server@1.1.0

The expected result is a JSON-RPC response containing the negotiated protocol version and server information. The server may also write a short status message to stderr. That status line is separate from the JSON-RPC response and should not be parsed as a tool result.

The release smoke test returned this server identity:

{
  "name": "devutils-mcp-server",
  "version": "1.1.0"
}

If the command cannot find npx, check node -v and npm -v in the same environment used by your MCP client. GUI clients can inherit a different PATH from your interactive shell.

Use the tools for bounded operations

Once connected, ask the assistant for a small, inspectable operation. For example:

Use the DevUtils hash_sha256 tool on the exact string hello and return only the hexadecimal digest.

The server registers tools in eight groups. The release README lists six hash tools, eight encoding tools, four generators, two JWT tools, three formatters, five converters, two network tools, and six text tools. Names follow a predictable <domain>_<operation> pattern.

For structured data, a useful request is:

Use json_validate on this JSON and explain the error location if it is invalid: { "enabled": true, }

For network data, use a non-sensitive example:

Use cidr_calculate for 192.168.10.0/24 and show the network, broadcast, host range, and host count.

These examples are intentionally bounded. The model chooses an explicit tool and supplies typed arguments, while the server performs the utility operation and returns text. You still need to inspect the result when it matters.

Why the MCP boundary helps

The value is not that a local library becomes faster through MCP. Native libraries are usually the right choice inside application code. The value is that an MCP client can call a consistent, typed operation during a multi-step conversation without inventing an implementation.

DevUtils uses the official TypeScript MCP SDK, Zod schemas for tool inputs, and stdio transport. The source registers each tool category with an McpServer before connecting a StdioServerTransport. That keeps the boundary explicit: the assistant can request a named operation, but it does not receive arbitrary code execution through this server.

The repository also keeps the package small enough to understand. The source is organized under src/tools/ by category, including hash.ts, formatters.ts, network.ts, and text.ts. That structure makes the project useful as a reference when you want to learn how a TypeScript MCP server wires schemas and handlers together.

Important limitations and security boundaries

DevUtils is a utility server, not a general security oracle.

The jwt_decode and jwt_validate tool descriptions explicitly say that they do not verify a JWT cryptographic signature. Decoding a token can help inspect its header and payload, but it does not prove that the token was issued by a trusted authority. Never treat a decoded payload as authenticated.

Hashing tools also have different purposes. MD5 and SHA-1 are available for compatibility and checksums, not for password storage. For passwords, use a dedicated password hashing scheme and an appropriate work factor. DevUtils includes bcrypt operations, but its presence does not remove the need to manage credentials, secrets, and authentication policy correctly.

The server runs locally through stdio and the security policy says it does not expose HTTP endpoints or send user data to external services. That is a useful boundary, not a universal privacy guarantee. The MCP client still receives the inputs you give it, npx still downloads a package before first use, and your machine still controls the process environment. Review the package, lock down client permissions, and avoid sending secrets in casual prompts.

The project is also not the best choice for every workload. If application code needs a hash, JSON parser, or CIDR calculation, use the native library directly. MCP adds a process and protocol boundary, which is valuable for agent workflows but unnecessary for a tight application loop.

FAQ

Does the server need an API key?

No API key is required by the documented package configuration. The server is started locally with Node.js and uses stdio.

Does it work with every AI assistant?

It works with MCP-compatible clients. The README documents Claude Desktop, Cursor, VS Code Copilot, Windsurf, Docker, and other MCP clients. A client without MCP support cannot use this server through the documented path.

Should I use the unpinned npx devutils-mcp-server command?

You can follow the README's short command, but a pinned version is better for a reproducible setup. Recheck the current release before upgrading.

Is JWT validation cryptographic verification?

No. The documented jwt_validate operation checks structure, JSON, expiration, and signature presence. It does not verify the signature against a key.

Takeaway

DevUtils MCP Server is a practical way to give an MCP-compatible assistant a small, local toolbox with explicit names and typed inputs. Start with the pinned v1.1.0 command, verify the initialize response, and then try one bounded operation such as JSON validation or SHA-256 hashing.

Have you found a developer utility that an AI assistant repeatedly gets wrong and that would benefit from a typed MCP tool?

AI assistance disclosure: I used AI assistance to organize and edit this tutorial. The commands, version details, configuration examples, and security boundaries were checked against the project's public documentation, source, release metadata, and a live initialize smoke test.