For Odoo 19 and higher, please review https://www.odoo.com/documentation/19.0/developer/reference/external_api.html

There is now a /doc endpoint that dynamically generates documentation on the models, fields and methods available for a specific database.

You might also want to know about the Odoo Language Server at https://github.com/odoo/odoo-ls that provides autocompletion, file validation, hover requests, go to definition, and more for VS Code, PyCharm, Vim and Zed.

My 2 cents on the topic. 
Some tipps for beginners (which would have been very helpful for me:

If you want to create a simple interface for JSON RPC and are lucky enough to have python:


The plane request to create it in a different language (here in postman):
1) get Authentication (Then the Credentials get stored as cookies, standard web auth)

where newstart9 is your database name and admin admin are your username and password

2) Then you can, like in rest, create update(write in odoo), delete like in REST

http://localhost:8069/web/dataset/call_kw/forum.post/create
{

"id": 5,

"jsonrpc": "2.0",

"method": "call",

"params": {

"model": "forum.post",

"method": "create",

"args": [

{

"name": "PowerPoint Karaoke",

"subtitle": "Die besten Erfindungen der Neuzeit"

}

]

}

Why Json-RPC is cool:
The permission concept of odoo is honored, that means you don't have to worry about it, if the user has permissions he get's the data if he doesn't he won't get it.

And most importantly you are not limited to create, update, you basically can do everything your user has permission to do. So together with minor odoo developments it's very easy to achive complex workflows compared to the very limited cumbersome REST capabilites where you need a lot of development to do basic things.

But of course you can't get Swagger/OpenAPI interface files for JSON-RPC, correct em if I'm wrong.

You could use 
https://github.com/OCA/rest-framework than you get swagger/OpenAPI Interface but you still have to create everything yourself. 

There are also some commercial Products 
https://apps.odoo.com/apps/modules/18.0/muk_rest should be good, but never really used it myself.

As a Bonus: if you only need to get access to data have a look at web_search_read, it's a not well documented feature of odoo which they use heavily inhouse. It's basically graphql for odoo. So you tell him exactly what you need spanning multiple related models and he gives you just that. If you have to do some more complex requirements - you will save yourself a lot of tears and work compared to an REST based approach not speaking of speed as you need for the same request a lot REST requests ...

NOTE: would have like to use the "commenting tool", but I don't have enough XP for that, so here is a non-answer :)

All the external ressources (tutorial, YouTube videos) are useful.

This is not enough, though: why the APIs does not have a clear auto-generated documentation? It makes it's usage overcomplicated. Also, the lack of examples makes things incredibly experimental. 

I had to rely on alternative documentation content from GitHub (created by the community, see link) to understand things. I think it could be reviewed by the Odoo team and merged to the existing doc. That would be very helpful for newcomers.

• https://github.com/amlaksil/Odoo-JSON-RPC-API/

It's also confusing and not clear why the "External API" and "Web Services" docs are separated.

• https://www.odoo.com/documentation/17.0/developer/reference/external_api.html#
• https://www.odoo.com/documentation/master/developer/howtos/web_services.html
  

(tried to use the "commenting tool", but that doesn't seem to work, so here is a non-answer:)

I can relate. We're migrating to Odoo DMS from Paperless, and this means I have to script the transfer of a couple tens of thousand documents, while preserving the metadata, such as tags, correspondents, notes, etc..

I've looked around but I cannot find a proper API description, nor any actual examples. It seems the external API is a simple wrapper around the models, but how do I get a list of models, and of the fields, and yes, it would really be useful to have an example of e.g. creating a DMS record with some tags and notes using the API.

Hi,
See this tutorial about json rpc in odoo:  Odoo JSON RPC

Thanks

Did you find any valuable documentation ? Looking for the same stuff without success

Hi,
Refer to the following documentation
https://www.cybrosys.com/blog/how-to-configure-the-json-rpc-api-in-odoo-15

https://www.cybrosys.com/blog/how-to-configure-json-rpc-and-xml-rpc-using-postman-for-sending-api-requests

Hope it helps