curl mcp - the last MCP you'll need

[!IMPORTANT] WORK IN PROGRESS

Requirements:

• Exposes simple REST API (with OpenAPI) as well as Remote MCP
• Easy to use through any MCP client, through API, and through browsers.
• X & GitHub OAuth
• Stripe credit deposit
• Contextual Instructions
• Markdown Transformation Proxy for popular websites such as X and GitHub
• Capped free use (per-hour ratelimit), pay as you go after hitting cap.
• Shareable instruction templates

My principles for making the LLM actually work well with tons of tools:

1. As the LLM knows popular websites, instruct it to simply use the web like normal.
2. Under water, ensure every input is somehow routed to the right substitute website(s).
3. Ensure every response is markdown and contains very few tokens, ideally less than 1000! This ensures we can do many steps.
4. Ensure the dead ends guide the LLM back on track.
5. Ensure every step in a multi-step process contains instructions about what to do next.
6. Ensure the path the LLM visit is the same as the path the user or crawler visits. Respond well on accept header and other information to distinguish.

How should product builders of today become ready to allow for this?

1. Most APIs use POST, but GET is easier to be instructed about, as it can be done in markdown. Let's promote making APIs GET and promote super easy to understand URL structures with minimal token length.
2. Ensure to use OpenAPI to show the possible endpoints and routing. Your API should be the first-class citizen, not your website.
3. Ensure to make your openapi explorable by either putting it right on the root at /openapi.json, or by putting redirecting to it from /.well-known/openapi if that's not possible.
4. Ensure all your pages that are exposed as text/html also expose a non-html variant (preferably markdown, or yaml if structured data can also be useful) that is under 1000 tokens with the same/similar functionality.
5. Hitting errors in your API should always guide the agent back on track, just like we do with humans. Try buildling these UX pathways on the API level!

Is it somehow possible to provide this as a middleware to APIs? For sure! The one tool to rule them all is curl (or fetch), and it could be made safe in the following way:

• Ensure to route away from human-first websites to ai-optimised websites.
• Ensure to truncate the response to never be above a certain limit
• Ensure to prefer accepting markdown

Usage

MCP Usage:

Install it into your MCP Client by adding the following to your config:

{
  "mcpServers": {
    "curlmcp": {
      "command": "npx",
      "args": ["mcp-remote", "https://curlmcp.com/sse"]
    }
  }
}

Browser Usage

The curlmcp api is easy to use from the browser too. Authentication is automatically handled.

CLI Usage

You can simply use curl yourself, or to have the curl mcp proxy:

• use curl -c cookies.txt https://curlmcp.com/login to login and store cookies
• use curl -b cookies.txt https://curlmcp.com/curl/{your-request}

API Usage: /curl/{url} Endpoint

The /curl/{url} endpoint allows you to send HTTP requests to any URL, mimicking the behavior of the curl command-line tool. It supports long-form query parameters to specify request details, such as the HTTP method, headers, and data.

Certain urls are configured to be proxied based on your configured template (defaults to default-proxy.yaml)

API Specification

GET /curl/{url}?request={method}&header={header}&data={data}&...

NB: {url} uses the https protocol by default.

Supported Query Parameters

Parameter	Type	Description	Example
request	string	Specifies the HTTP method. Valid values: GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS.	request=POST
header	array of strings	Adds custom HTTP headers. Repeat for multiple headers.	header=Content-Type:application/json
data	array of strings	Sends data in the request body (POST) or query string (with get=true). Repeat for multiple data pairs.	data=key=value
data-urlencode	array of strings	Sends URL-encoded data in the request.	data-urlencode=comment=this%20is%20awesome
get	boolean	Forces data to be sent as a GET request query string.	get=true
include	boolean	Includes response headers in the output.	include=true
head	boolean	Sends a HEAD request.	head=true
user	string	Specifies credentials for authentication (format: username:password).	user=user:pass
location	boolean	Follows HTTP redirects.	location=true
verbose	boolean	Enables verbose output for debugging.	verbose=true
access_token	string	Injects an OAuth token for X or GitHub authentication.	access_token=xyz
instructions	string	Specifies contextual instructions for the request.	instructions=transform_response_to_markdown

Links

• Previous attempt (curl api): https://github.com/janwilmake/curlapi
• Previous attempt (fetch mcp): https://github.com/janwilmake/fetch-mcp