This is because you have (accidentally) used "tuple typing". This is enabled when the value of "items" is an array, and it matches schemas to specific positions in the array.

If you change "items" (in your schema) to be simply a schema (not an array of schemas), then it will validate all items the same way.

I asked this same question on the JSON schema google group, and it was answered quickly. User fge asked that I post his response here:

Hello,

The current specification is draft v4, not draft v3. More specifically, the validation specification is here:

https://datatracker.ietf.org/doc/html/draft-fge-json-schema-validation-00

The web site is not up to date, I don't know why... I'll submit a pull request.

With draft v4 you can use this:

{
    "type": "array",
    "items": {
        "oneOf": [
            {"first": [ "schema", "here" ] }, 
            {"other": [ "schema": "here" ] }
        ]
    }  
}

For instance, this is a schema for an array where items can be either strings or integers (it can be written in a more simple way though):

{
    "type": "array",
    "items": {
        "oneOf": [
            {"type": "string"},
            {"type": "integer"}
        ]
    }
}

This is the correct answer. My corrected schema now includes:

"transactions" : {
    "type" : "array",
    "items" : {
        "oneOf" : [
            {
                "type" : "object",
                "properties" : {
                    "type" : {
                        "type" : "string",
                        "enum" : ["BUILD", "REASSIGN"]
                    }
                }
            },
            {
               "type" : "object",
               "properties" : {
                 "type" : {
                   "type" : "string",
                   "enum" : ["BREAK"]
                  }
               }
            }
        ]
    }
}

You've got the basic idea of using enum to separate what's matching, but there are a couple of mistakes here:

• Json schema arrays don't have properties, they have items.
• Within those properties you're defining name as an attribute that then holds other json schema objects.
• In the second branch of your schema you defined otherProperty3 but in your sample that property is called anotherProperty3

Try this slightly modified version:

{
"$schema": "http://json-schema.org/draft-04/schema#",
"type": "object",
"required": ["items"],
"properties": {
    "items": {
        "type": "array",
        "minItems": 1,
        "additionalProperties": false,
        "items": {
            "anyOf": [
                {
                    "type": "object",
                    "required": ["name", "otherProperty"],
                    "additionalProperties": false,
                    "properties": {
                        "otherProperty": { "type": "string" },
                        "name": { "enum": [ "foo" ] }
                    }
                },{
                    "type": "object",
                    "required": ["name", "otherProperty2", "anotherProperty3" ],
                    "additionalProperties": false,
                    "properties": {
                        "otherProperty2": { "type": "string" },
                        "anotherProperty3": { "type": "string" },
                        "name": { "enum": [ "foo2" ] }
                    }
                }
            ]
        }
    }
}
}