The "meta"-section is necessary for assigning the internal declaration of the entities in your CRM system to generic attributes in the mapping. (Every entity that is declared in meta will be included in the FieldDefinitions when downloaded, provided they exist in the CRM. ) –> "fielddefinitions" : {} Depending on the CRM there are various attributes which must be provided.

Syntax Example (Salesforce) 
"meta": {
  "cRM Entity1": {
    "apiName": "CRM Entity1",
    "idProperty": "Id",
    …
  },
  "cRM Entity2": {
    "apiName": "CRM Entity1",
    "idProperty": "Id",
    …
  },
  …
}
 
"meta": {
  "lead": {
    "apiName": "Lead",
    "idProperty": "Id"
  },
  "contact": {
    "apiName": "Contact",
    "idProperty": "Id"
  },
  "account": {
    "apiName": "Account",
    "idProperty": "Id"
  },
  "campaignMember": {
    "apiName": "CampaignMember",
    "idProperty": "Id"
  },
  "task": {
    "apiName": "Task",
    "idProperty": "Id"
  }
}

All available entity properties

Name Description Example
apiName Name of the entity in the CRM "Lead"
idProperty Unique Identifier (Internal) "Id"
logicalName Same as cRM entity "lead"
allowedActions Defines which actions are allowed for the entity 
"allowedActions": {
    "create": false,
    "update": true
}
invalidations Throw an error message when the condition is true 
"invalidations": {
    "create": [
        {
            "message": "This is not allowed!",
            "condition": "{{ mergedItem.RecordType=='1000101' }}"
        }
    ]
}