App Gen with REST APIs that have no OpenAPI schema — how do you handle it?

💬 App Building
1

Hey everyone,

I've been playing with Retool's App Gen feature. What I'm not really clear on: how do you feed an API that only has HTML docs (no OpenAPI/Swagger schema) into App Gen / Assist?

The REST API resource in Retool can import an OpenAPI schema — but what if the only API documentation is an HTML page? I feel like I'm missing a step here.

Are you manually writing an OpenAPI spec for it? Using tools to convert HTML docs to a spec? Or just writing the queries by hand?

Would love to hear how you handle this :+1:

4

Hey, thanks for writing in! @mascaritas It's great to hear you have been trying out Retool Assist, ever since then we've launched our new app builder! Have you tried it yet? It's designed to make building apps much faster, and like Assist, it works best when your REST API resource has an OpenAPI spec attached so it understands your endpoints.

The quickest way to get there: paste your HTML docs into an LLM and ask it to generate an OpenAPI 3.0 YAML/JSON spec. Then upload it to your REST API resource config under "Use an API spec". Once attached, the new app builder can autocomplete endpoints and properties correctly.

Let me know if that works well for you, thanks! :folded_hands:

5

Hello again @mascaritas, how's it going? Was my answer above helpful? Let me know! :+1:

6

Hi CHiEn

yes, I asked the provider of said API for such a schema, as soon as I have it I ll implement

7

Hey @mascaritas, sounds good! Let me know how it goes after you implement it!

8

Hey, just wanted to add something from the other side of this problem. I build and maintain OpenAPI specs for a few APIs, and the biggest issue is usually not the missing spec itself, it is getting the spec accurate once it exists.

If you end up asking an LLM to generate the YAML/JSON from docs, double check these parts manually:

  • Required vs optional parameters (AI often marks things optional that are actually required)
  • Response schema types (numbers get typed as strings a lot)
  • Enum values for fields that only accept fixed options
  • Example values for each parameter, this is what really helps autocomplete work well in app builders

Once the spec is clean, tools like Retool's new app builder pick up endpoints and fields correctly and save a lot of manual setup time. Good luck once you get the schema from your provider.