Assitance API JSON response is valid but contains invalid characters

I have created a simple Assistance where I want it to convert the input into a valid JSON output. At first, I tried the direct approach which is this.
Convert the input message into following JSON Format without changing anything.
{
“Overall Summary”: {
“comment”: “”,
},
“Strength1”: {
“comment”: “”,
},
“Strength2”: {
“comment”: “”,
},
“Strength3”: {
“comment”: “”
}
}
When it didnt work I added a function calling instead
{
“model”: “gpt-4”,
“instructions”: "Convert the input message into JSON Format without changing anything. Imporant: always use the response tool to respond to the user.Never add any other text to the response. ",
“tools”: [
{
“type”: “function”,
“function”: {
“name”: “response”,
“description”: “Translate user input into JSON Format”,
“parameters”: {
“type”: “object”,
“required”: [
“OverallSummary”,
“strength1”,
“strength2”,
“strength3”
],
“properties”: {
“OverallSummary”: {
“comment”: “”
},
“strength1”: {
“comment”: “”
},
“strength2”: {
“comment”: “”
},
“strength3”: {
“comment”: “”
}
}
}
}
}
]
}
In both the scenario I am getting valid JSON but it contains invalid backward slash characters
{\n "OverallSummary": "John has demonstrated exceptional capabilities throughout the project, showcasing independence, autonomy, and a strong ownership in solving problems and managing tasks. Her approach to client interaction is noteworthy, often receiving direct appreciation from clients for her maturity and professionalism. Despite initial challenges with managing stress during presentations, John has shown significant improvement, remaining calm and effective under pressure. Her ability to drive content and processes, alongside her senior behavior and communication skills, aligns well with her role as a consultant. John’s practical and effective approach in handling both long-term and short-term streams, her structured and autonomous management of various sub-streams, and her commitment to going above and beyond in supporting her team are commendable.",\n "strength1": "John has excelled in solving a wide range of problems independently and with minimal leadership support, showcasing a strong analytical ability and insight.",\n "strength2": "",\n "strength3": ""\n }\n}

Both scenarios work fine in playground. However, when I do API calls using POSTMAN I get above response. Does anyone know how to get a valid response.