When connecting to LUIS, what does the "forceset" parameter do - azure-language-understanding

Question

In my LUIS app I have an intent called GetWeather requiring a Location to be set.
When connecting to the app using the query
What is the weather in london
it correctly returns
{
"query": "what is the weather in london",
"topScoringIntent": {
"intent": "GetWeather",
"score": 0.999875546,
"actions": [
{
"triggered": true,
"name": "GetWeather",
"parameters": [
{
"name": "Location",
"type": "Location",
"required": true,
"value": [
{
"entity": "london",
"type": "Location",
"resolution": {}
}
]
}
]
}
]
},
"entities": [
{
"entity": "london",
"type": "Location",
"startIndex": 23,
"endIndex": 28,
"score": 0.832388461,
"resolution": {}
}
],
"dialog": {
"contextId": "e1df6c2d-e691-4fc6-89f2-3ee2ef519724",
"status": "Finished"
}
}
If I instead use the query
What is the weather
It returns the following expected result.
{
"query": "what is the weather",
"topScoringIntent": {
"intent": "GetWeather",
"score": 1.0,
"actions": [
{
"triggered": false,
"name": "GetWeather",
"parameters": [
{
"name": "Location",
"type": "Location",
"required": true,
"value": null
}
]
}
]
},
"entities": [],
"dialog": {
"prompt": "Where",
"parameterName": "Location",
"parameterType": "Location",
"contextId": "3b0725f4-7d6f-43fd-ab6e-02fc11c3eed1",
"status": "Question"
}
}
I thought that using the contextID together with the forceSet parameter in my next call would set the parameter Location to whatever I send as the query. The conection string I use is this:
https://api.projectoxford.ai/luis/v2.0/apps/{APP_ID}?subscription-key={SUBSCRIPTION_KEY}&q=london&contextid=3b0725f4-7d6f-43fd-ab6e-02fc11c3eed1&forceset=Location
Instead I get the following response back:
{
"query": "london",
"topScoringIntent": {
"intent": "GetWeather",
"score": 1.0,
"actions": [
{
"triggered": false,
"name": "GetWeather",
"parameters": [
{
"name": "Location",
"type": "Location",
"required": true,
"value": null
}
]
}
]
},
"entities": [],
"dialog": {
"prompt": "Where",
"parameterName": "Location",
"parameterType": "Location",
"contextId": "3b0725f4-7d6f-43fd-ab6e-02fc11c3eed1",
"status": "Question"
}
}
I had expected to get something like my first response back.
Am I doing something wrong or just misunderstanding what the forceSet parameter is supposed to do?