diff --git a/README.md b/README.md
index 7d19c90..73dfe7a 100644
--- a/README.md
+++ b/README.md
@@ -61,6 +61,12 @@ Rollback to specific migration, use `list` command to see (Pending) changes:
 
 To re-apply changes again, simply do a `database update` again. Beware that data will be lost.
 
+When this error appears:
+
+`Unable to create a 'DbContext' of type 'RuntimeType'. The exception 'The configuration file 'appsettings.json' was not found and is not optional.`
+
+Then you should either provide an `appsettings.json` file in the project, or simply change the startup project.
+
 ## Links
 
 * [Entity Framework - Database providers](https://learn.microsoft.com/en-us/ef/core/providers/?tabs=dotnet-core-cli)
@@ -203,3 +209,17 @@ To run this tool:
 * `dotnet aspnet-codegenerator controller -name TeamsController -async -api -m Team -dc DeadBallZoneLeagueDbContext -outDir Controllers -dbProvider sqlite`
 
 Note that an issue may arise, related to this: https://github.com/dotnet/Scaffolding/issues/3145
+
+## API
+
+Since .NET 9, the OpenAPI standard has been defined. To view documentation of our API, Swagger UI can be installed separately.
+
+See also: https://devblogs.microsoft.com/dotnet/dotnet9-openapi/
+
+* [https://swagger.io/tools/swagger-ui/](https://swagger.io/tools/swagger-ui/)
+
+* [Swagger UI installation](https://github.com/swagger-api/swagger-ui/blob/HEAD/docs/usage/installation.md)
+
+Or use:
+
+* [install-swagger-tooling](https://learn.microsoft.com/en-us/aspnet/core/tutorials/first-web-api?view=aspnetcore-9.0&tabs=visual-studio-code#install-swagger-tooling)
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