Terraform: Unsupported attribute when referencing output variables - terraform

Question

I have a question regarding terraform. I have the following setup:
rds/
main.tf
variables.tf
imports.tf
outputs.tf
database-service.tf
main.tf
variables.tf
imports.tf
outputs.tf
I have inside the rds folder my basic rds terraform scripts (as a module) which I want to use inside the database-service.tf file.
Inside the rds/outputs.tf are the following outputs defined:
output "foo-aurora-db-endpoint" {
description = "foo DB Endpoint"
value = aws_rds_cluster.foo_db_default.endpoint
}
output "foo-aurora-db" {
description = "foo DB"
value = aws_rds_cluster.foo_db_default
}
output "foo-aurora-db-port" {
description = "foo DB Port"
value = aws_rds_cluster.foo_db_default.port
}
These values are referenced inside the outputs.tf:
output "foo-aurora-db-endpoint" {
value = module.foo-db.foo-aurora-db-endpoint
}
output "foo-aurora-db-port" {
value = module.foo-db.foo-aurora-db-port
}
My database-service.tf looks like this:
module "foo-db" {
source = "./rds"
...
}
A snippet of my rds/main.tf file
resource "aws_rds_cluster" "foo_db_default" {
cluster_identifier = var.cluster_identifier
availability_zones = ["eu-central-1a", "eu-central-1b", "eu-central-1c"]
database_name = var.database_name
master_username = var.master_username
master_password = var.master_password
engine = var.database_engine
skip_final_snapshot = true
db_subnet_group_name = aws_db_subnet_group.foo_db_default.name
vpc_security_group_ids = [aws_security_group.foo_db_rds.id]
}
When I now run terraform plan or apply I get the following error
Error: Unsupported attribute
on outputs.tf line 35, in output "foo-aurora-db-endpoint":
35: value = module.foo-db.foo-aurora-db-endpoint
This value does not have any attributes.
What am I missing?
Edit: When referencing module.foo-db inside the outputs.tf I get the following output:
foo-aurora-db-endpoint = [
{
"foo-aurora-db-endpoint" = "<endpoint value>"
"foo-aurora-db-password" = "<password>"
"foo-aurora-db-port" = <port>
"foo-aurora-db-username" = "<username>"
},
]
But I can't figure out how to reference them.