How to set custom error message in jsonschema if/else

I have a JSON schema like this:

{
  "authentication": {
    // provider is an enum. Let's say it has A and B as values.
    // if A is chosen, jwt must have a value.
    // if B is chosen, jwt must NOT have a value
    // Let's say JWT has 3 requirede properties. audience, issuer, and baz
    "provider": "B",
    "jwt": { "audience": "foo", "issuer": "bar" }
  }
}

This is my current validation:

"allOf": [
  {
    "$comment": "We want the user to provide the JWT property when the provider requires it",
    "if": {
      "properties": {
        "provider": {
          "anyOf": [
            { "const": "A" },
          ]
        }
      },
      "required": ["provider"]
    },
    "then": {
      "required": ["jwt"]
    }
  },
  {
    "$comment": "We want JWT property to be null when a provider does not require it. This reduces bugs and confusion.",
    "if": {
      "properties": {
        "provider": {
          "not": {
            "anyOf": [
              { "const": "A" }
            ]
          }
        }
      },
      "required": ["provider"]
    },
    "then": {
      "properties": {
        "jwt": {
          "type": "null"
        }
      }
    }
  }
]

This works, but it isn't a great experience:

• There's a warning about jwt: Missing property "baz".
• There are warnings about audience and issuer: Incorrect type. Expected "null".

The only error that would make sense would be that jwt should not have a value because of the chosen provider. This is represented by Incorrect type. Expected "null"., but it isn't obvious enough.

So, my questions:

• How can I set custom error messages in if/else?
• Any tips to get rid of the "missing baz property", which is irrelevant anyway as the parent property (jwt) shouldn't exist anyway?

This doesn't provide custom error output, but the output is much cleaner

Basically, you only check for the fail condition, if B then disallow jwt. Otherwise, require jwt and the root schema provides the constraints for jwt.

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": ["authorization"],
  "properties": {
    "authorization": {
      "required": ["provider"],
      "properties": {
        "provider": {"type": "string"},
        "jwt": {
          "required": ["audience", "issuer", "baz"],
          "properties": {
            "audience": {},
            "issuer": {},
            "baz": {}
          }
        }
      },
      "allOf": [
        {
          "if": {
            "properties": {
              "provider": {"const": "B"}
            } 
          },
          "then": {
            "properties": {"jwt": false}
          },
          "else": {
            "required": ["jwt"]
          }
        }
      ]
    }
  }
}

the only difference between null and disallowed would be changing the then statement

      "then": {
        "properties": {
          "jwt": {
            "const": null
          }
        }
      }

authorization:
  provider: A
  jwt:
    audience: true
    issuer: true
    baz: true

authorization:
  provider: B

authorization:
  provider: B
  jwt: null