devpack MCP Server: Dev Tools for Claude, ChatGPT & Cursor
Give your AI assistant devpack.app’s developer tools. Connect the free devpack MCP server to Claude, ChatGPT, Cursor or any other MCP client, then ask it to format JSON, decode a JWT, explain a cron schedule or check a site’s SSL, DNS, headers and meta tags, right in the chat. No sign-up, no API key.
Server URL
https://mcp.devpack.appTransport: Streamable HTTP. Authentication: none. https://devpack.app/mcp works too.
Connect from Claude
- In Claude on the web or desktop, open Settings → Connectors.
- Click Add custom connector.
- Name it devpack, paste
https://mcp.devpack.appas the URL and click Add. - In a chat, open the tools menu and turn on devpack.
In Claude Code, run:
claude mcp add --transport http devpack https://mcp.devpack.appConnect from ChatGPT
- Open Settings → Apps & Connectors → Advanced settings and turn on Developer mode.
- Back in Apps & Connectors, click Create.
- Name it devpack, paste
https://mcp.devpack.appas the MCP server URL, choose No authentication and click Create. - In a chat, pick devpack from the + menu.
Custom connectors need a paid ChatGPT plan, and menu names change from time to time.
Connect from Cursor
Open Cursor Settings → MCP → Add new MCP server, or add devpack to ~/.cursor/mcp.json (or .cursor/mcp.json in a project):
{
"mcpServers": {
"devpack": { "url": "https://mcp.devpack.app" }
}
}Other MCP clients
VS Code reads .vscode/mcp.json:
{
"servers": {
"devpack": { "type": "http", "url": "https://mcp.devpack.app" }
}
}Windsurf, Zed, Cline and other clients take the same URL as a remote (Streamable HTTP) server. A client that only runs local servers can connect through npx mcp-remote https://mcp.devpack.app.
Tools
Each MCP tool does the same job as a devpack page. Open the page to work with the result in your browser.
| MCP tool | What it does | On devpack |
|---|---|---|
format_json | Validate JSON and pretty-print or minify it. Invalid JSON returns valid: false with the parse error. | JSON Formatter |
decode_jwt | Decode a JSON Web Token’s header and payload and report its issued, not-before and expiry times. Does not verify the signature. | JWT Decoder |
verify_jwt | Verify an HMAC-signed JWT (HS256, HS384, HS512) with its secret and check whether it has expired. | JWT Decoder |
hash_text | Hash text with MD5, SHA-1, SHA-256, SHA-384 or SHA-512. | Hash Generator |
hmac_sign | Create an HMAC signature of a message with a secret, for example to sign or check a webhook. | HMAC Generator |
base64 | Encode text to Base64 or decode Base64 to text, with the standard or URL-safe alphabet. | Base64 Encode / Decode |
url_encode | Percent-encode text for a URL, or decode percent-encoding. | URL Encode / Decode |
convert_yaml | Convert YAML to JSON or JSON to YAML. Reports the parse error when the input is invalid. | YAML to JSON |
csv_to_json | Convert CSV text to a JSON array, using the first row as keys by default. | CSV to JSON |
query_json_path | Run a JSONPath expression (such as $.items[*].id) against JSON and return the matching values. Filter expressions are not supported. | JSONPath Tester |
test_regex | Run a JavaScript regular expression against text and list every match with its index and capture groups. | Regex Tester |
diff_text | Compare two texts line by line and return a unified diff with the number of added and removed lines. | Diff Checker |
format_sql | Format a SQL query for a chosen dialect, with upper- or lowercase keywords. | SQL Formatter |
markdown_to_html | Convert Markdown, including GitHub-flavored tables and task lists, to HTML. | Markdown to HTML |
convert_case | Change text to lower, upper, title, sentence, camelCase, PascalCase, snake_case, kebab-case or CONSTANT_CASE. | Case Converter |
generate_uuid | Generate random version 4 UUIDs. | UUID Generator |
generate_password | Generate strong random passwords with a chosen length and character sets. | Password Generator |
generate_qr_code | Generate a QR code for a URL or text. Returns the QR code as an image and as SVG markup. | QR Code Generator |
convert_timestamp | Convert between Unix time (seconds or milliseconds) and ISO 8601 dates. Without a value it returns the current time. | Unix Timestamp Converter |
explain_cron | Explain a five-field cron expression in plain English and list its next run times (UTC). | Cron Expression Generator |
convert_color | Convert a color between hex, RGB and HSL. | Color Converter |
check_color_contrast | Check the WCAG contrast ratio of a text color on a background color, with AA and AAA results. | Contrast Checker |
calculate_subnet | Calculate an IPv4 subnet from CIDR notation: network, broadcast, netmask, host range and host count. | Subnet Calculator |
http_status | Look up the name and class of an HTTP status code, with a link to its full explanation. | HTTP Status Codes |
seo_audit | Run an on-page SEO audit of a public URL: an overall score, scores by category and every issue with how to fix it. | SEO Checker & Site Audit |
check_meta_tags | Fetch a public page and read its title, meta description, canonical URL, robots tag, Open Graph and Twitter card tags. | Meta Tag Checker |
check_link_preview | Check how a link previews on social apps and chat: Open Graph and Twitter tags, the preview image and problems to fix. | Open Graph Checker |
validate_schema_markup | Read and validate the structured data (JSON-LD, microdata, RDFa) on a public page or in pasted HTML or JSON-LD. | Schema Markup Validator |
check_security_headers | Fetch a public URL, list its HTTP response headers and grade its security headers (HSTS, CSP, X-Frame-Options and more). | Security Headers Checker |
check_cors | Test a URL’s CORS response for a calling origin, method and request headers, including the preflight, and explain what fails. | CORS Tester |
check_redirects | Follow a URL’s redirect chain hop by hop, with each status code and the final URL. | Redirect Checker |
check_ssl | Check a host’s TLS certificate: issuer, validity dates, days left and the names it covers. | SSL Checker |
check_website_status | Check whether a public website responds, with its status code and response time. | Website Down Checker |
check_robots_txt | Read a site’s robots.txt and test whether a path is allowed for Googlebot, AI crawlers or a given user agent. | Robots.txt Tester |
check_ai_crawlers | Check which AI crawlers (GPTBot, ClaudeBot, PerplexityBot, Google-Extended and more) a site allows, and whether it has llms.txt. | AI Crawler Checker |
check_sitemap | Find and read a site’s XML sitemap (from robots.txt or a sitemap URL), optionally checking the status of up to 50 of its URLs. | Sitemap Validator |
dns_lookup | Look up DNS records (A, AAAA, CNAME, MX, TXT, NS, SOA, CAA, SRV, PTR) for a domain. | DNS Lookup |
check_dns_propagation | Check a DNS record on public resolvers around the world to see whether a change has propagated everywhere. | DNS Propagation Checker |
check_email_dns | Check a domain’s MX, SPF and DMARC records and flag common setup problems. | SPF, DKIM & DMARC Checker |
whois_lookup | Look up a domain’s or IP address’s registration data (RDAP): registrar, dates, status and name servers. | WHOIS Lookup |
Things to ask
- “Is this JSON valid? Format it.”
- “Decode this JWT and tell me when it expires.”
- “When does
0 9 * * 1-5run next?” - “Check the SSL certificate and security headers of example.com.”
- “Does example.com have SPF and DMARC set up?”
- “Is GPTBot allowed to crawl example.com?”
Limits and privacy
The MCP server shares the free plan of the devpack API: 60 calls a minute for text and data tools, 15 a minute for website checks and 1,000 a day, counted per IP address. When a limit is reached, the tool says so and your assistant can try again a minute later.
Inputs are used to answer the call and are not stored. Website checks fetch only public URLs; private and local addresses are refused, and requests identify themselves as DevPackBot. Details are in the Privacy Policy.
Questions
What is an MCP server? MCP (Model Context Protocol) is an open standard that lets AI assistants call outside tools. The devpack MCP server makes devpack’s developer tools available to any assistant that supports it.
Is it free? Yes. It needs no account or API key, within the limits above.
Which AI apps work with it? Claude (web, desktop and Claude Code), ChatGPT with Developer mode, Cursor, VS Code, Windsurf and any other client that supports remote MCP servers over Streamable HTTP.
What happens to the data my assistant sends? Your assistant sends only the text or URL it needs to check. devpack returns the result and does not store the input.
Can I call the same tools from my own code? Yes. Every MCP tool wraps an endpoint of the free devpack REST API. Prefer the browser? Browse all tools.