Show HN: Reverse-engineering web apps into agent tools

Hey HN! We built a browser-based agent that runs inside an authenticated web app, watches how the app calls its own APIs, and automatically turns those into agent tools. You can think of it as an auto-generated MCP server that self-updates as the host app changes.

The result is a skilled AI assistant that actually integrates deeply with any product (not just chat and RAG) with minimal effort.

Check out these short demos below that show the agent in software you're probably familiar with:

- Jira: https://demo.frigade.com/hn?skill=jira

- Spotify: https://demo.frigade.com/hn?skill=spotify

- Hacker News (lol): https://demo.frigade.com/hn?skill=hackernews

- Full Demo: https://demo.frigade.com/hn?skill=full-demo

As you can see in the examples, you can do way more (and faster) than what you normally would be able to via point and click. And we never even touched the source code of these products!

Why do this?

In an ideal world, every application has an MCP server or an easily-digestible API available for AI agents to feed from. In practice, we found that even very modern software tends to have a spider web of confusing APIs and services that AI agents simply cannot use out of the box. Security also becomes a huge issue as applications have different (often homebrewed) standards for how endpoints are secured (JWTs/cookies/mix of both). Finally, having an actual browser agent go in and use the application on behalf of the user (i.e. computer-use), is simply too brittle, slow, and burns a lot of tokens.

We took our existing browser agent that’s already trained to use and learn authenticated applications, and added an extra step that automatically turns the app’s authenticated APIs into "recipes". A recipe is a mix of the following:

- API endpoint + method

- Authentication method (and how to retrieve refresh auth tokens/cookies)

- Response schema

- Input schema (for POST/PUT)

- Human readable description of what the tool does

Putting it all together, these become reusable tools for LLMs, all without writing or maintaining any code. Even if the APIs change our agent figures this out and replaces the recipe for the tool with the updated version.

Adding tools to an AI agent becomes super simple this way:

- Our agent trains on the app and builds the recipes

- The app owner enables discovered tools from our dashboard

- The agent can now take actions on the user’s behalf directly inside the application. For instance, saying something like "invite my teammate to my workspace" would securely call the existing API endpoint for inviting users without proxying or relaying through a third party.

Of course, there's a ton of edge cases you run into when you try to do this - every application is intrinsically different despite how many "standards" exist. Fun fact: graphql was by far the worst API to work with in standardizing the recipes.

Looking forward to your feedback/comments!

71 points | by pancomplex 1 day ago

17 comments

  • arjunchint 11 minutes ago
    I am not following a couple of things:

    - you sell to websites an in-app agent

    - why not just have them give you API spec, why reverse engineer their APIs?

    A bit longer term, would you see yourself competing with WebMCP then? Because the website can just expose those APIs to any browser agent

    • pancomplex 3 minutes ago
      Even with an API spec it wouldn't "just work". You'd still need to handle authentication and have a place to manage which APIs you want the in-app agent to have access to / when to call a given tool.

      And believe it or not, even big companies with big companies don't have API specs available for their applications ¯\_(ツ)_/¯

  • nixus76 4 hours ago
    Very cool! Does it require some kind of scraping of a third party web app, like clicking through with a browser agent? If so, how can I be sure it does not delete my account or subscribe to another plan or make some other destructive actions if I allow it to do that with my authed acct?
    • pancomplex 3 hours ago
      We use a browser-based agent to learn all the APIs and turn them into skills. Most users will run this in a staging/test account to create all the recipes/blueprints. Our agent is also instructed to not take any destructive actions - but of course LLMs make mistakes (hence the test account :) ).

      You can see more about how it works in detail here: https://frigade.com/how-it-works

      • nixus76 1 hour ago
        Got it- so it is "inside-out", not "outside-in" kind of product. Very impressive either case, congrats!

        How does it work with the intercom widget though?

        • pancomplex 36 minutes ago
          You don't need an intercom widget - we supply the widget / primary point of interaction. No need to talk to humans anymore!
  • hajimuz 12 hours ago
    This is really helpful. I usually manually do this with chrome dev tools, it’s kind of tedious especially the header and cookies handling.
    • pancomplex 3 hours ago
      Agreed - and especially when the API changes..
  • west_subject 17 hours ago
    Is this opensource ? like the tool itself ? in it's entirety ??
    • pancomplex 17 hours ago
      Not at this point - but we’re considering it! What would you use it for?
      • Synthetic7346 16 hours ago
        Gas and energy utility portal
      • west_subject 14 hours ago
        make product demo videos, plus extend the functionality to save and contain repetitive task inside any app and have that run at some trigger.
  • robszumski 1 day ago
    Really cool. It would be interesting to see a demo of an app that is clearly more bespoke, like your Tesla account, online banking, movie theatre ticketing, etc.
  • akash91 12 hours ago
    Which LLM model is it using?
    • pancomplex 5 hours ago
      Works with any frontier LLM model
  • zenniskayy 21 hours ago
    Very cool project. Looking forward to trying it.
  • dodobirdy 1 hour ago
    Now this is something truly agentic.
  • spzb 9 hours ago
    You want me to run a closed source, LLM agent inside my browser with access to authenticated API endpoints ?! Thanks but no thanks.
    • pancomplex 5 hours ago
      No definitely not!

      Our customers run the training on their own applications using a demo or staging environment. Then they install the in-app agent you see in the demos and turn on the tool calls they like. All the API calls are executed client side and never touches any of our servers.

    • katemaster009 9 hours ago
      But maybe we if have more clarity on how it is working under the hood, then maybe we trust it. For me its kind of pattern - too many if's but's and maybe's on all the new tools i want to use.
  • Priyansh7 13 hours ago
    Cool project
  • reaganhsu 1 day ago
    so cool!
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