Developer tools for AI agents (MCP)

The tools from this site, packaged as a local Model Context Protocol server. Claude, Cursor and other AI assistants can then format and query JSON, validate schemas, verify JWTs, hash files and convert timestamps exactly, instead of guessing.

Version 0.1.0
Runs on your computer, no network access
Free

Install

Claude Desktop

Download devtoolbox-0.1.0.mcpb (devtoolbox.cc tools as a Claude Desktop extension).
Open the file with Claude Desktop: double-click it, or drag it onto Settings → Extensions.
Click Install. Claude Desktop comes with Node.js; nothing else is needed.

Claude Code

Run this in a terminal (Node.js 20 or newer):

claude mcp add devtoolbox -- npx -y https://devtoolbox.cc/downloads/devtoolbox-mcp-0.1.0.tgz

Cursor, VS Code, Windsurf and other MCP clients

Add the server to the client's MCP configuration (for Cursor, ~/.cursor/mcp.json). It needs Node.js 20 or newer.

{
  "mcpServers": {
    "devtoolbox": {
      "command": "npx",
      "args": [
        "-y",
        "https://devtoolbox.cc/downloads/devtoolbox-mcp-0.1.0.tgz"
      ]
    }
  }
}

VS Code uses the key "servers" instead of "mcpServers" in.vscode/mcp.json.

Tools

Each tool uses the same code as the tool on this site, so results are identical.

Tool	What it does	On the web
`json_format`	Validate, pretty-print, minify or sort JSON, with exact error positions and exact big numbers.	JSON Editor
`jsonpath_query`	Run an RFC 9535 JSONPath query on JSON text or a file; get values, paths or both.	JSONPath
`json_schema_validate`	Validate JSON against a JSON Schema (drafts 4, 7, 2019-09, 2020-12), with error paths.	JSON Schema
`json_diff`	Structural diff of two JSON documents or files, with array modes and an RFC 6902 patch.	JSON Diff
`json_convert`	Convert between JSON, YAML and CSV without silent type changes.	JSON / YAML / CSV
`hash`	MD5, SHA-1, SHA-256, SHA-384 and SHA-512 digests or HMACs of text or a file.	Hash
`jwt_decode_verify`	Decode a JWT, check exp/nbf/iat and verify its signature with a secret, PEM or JWK.	JWT Debugger
`jwt_sign`	Create a signed JWT (HS, RS, PS or ES algorithms) for testing.	JWT Debugger
`timestamp_convert`	Unix timestamp ↔ date in any time zone; detects s/ms/µs/ns and daylight-saving gaps.	Timestamp
`uuid`	Generate v4 or v7 UUIDs (up to 1,000), or read the version, variant and time of one.	UUID
`base64`	Encode or decode Base64 (standard or URL-safe) for text or files.	Base64
`number_base`	Convert integers of any size between bases 2–36, with two's complement.	Number Base
`url`	Percent-encode or decode text, or split a URL into its parts and query parameters.	URL Encode
`qr_code`	Make a QR code as SVG for text, a URL or a Wi-Fi network.	QR Code
`image_base64`	Turn an image file into a data URI, or Base64 back into an image file.	Image ↔ Base64

Things to ask

"Validate orders.json against orders.schema.json and list the errors."
"Which customers in export.json have refunded orders? Use JSONPath."
"Compare config.old.json and config.json, ignoring array order."
"Is this JWT expired, and does it verify with the key in public.pem?"
"What's the SHA-256 of release.zip?"
"Convert users.csv to YAML and save it as users.yaml."

Privacy and safety

The server runs on your computer and makes no network requests. Your files, tokens and keys never reach devtoolbox.cc or anyone else.
It reads a file only when a tool is given its path (absolute paths work best).
It writes a file only when asked to save a result (output_path), and never replaces an existing file unless told to.
Keys and secrets can come from a file or an environment variable, so they don't have to be pasted into the chat.

Files, checksums and updates

devtoolbox-0.1.0.mcpb: Claude Desktop extension
devtoolbox-mcp-0.1.0.tgz: npm package, used by the commands above
SHA256SUMS: checksums to verify a download (sha256sum -c SHA256SUMS)

Both files contain a single JavaScript file with all dependencies included, plus the licences of the open-source packages it uses. To update, install again from this page when the version number changes.