Hi. I'm trying to define a parameterized access policy to give a practitioner access only to some users. My access policy looks like this:

"resourceType": "AccessPolicy",
  "name": "Parameterized Patient Access Policy ",
  "resource": [
    {
      "resourceType": "Patient",
      "criteria": "Patient?_id=%user_id"
    }

I've also modified the project membership:

"access": [
    {
      "policy": {
        "reference": "AccessPolicy/d777cbc1-5994-42da-a2f4-09f5e763497f"
      },
      "parameter": [
        {
          "name": "user_id",
          "valueReference": {
            "reference": "3e58c06e-c2da-447c-a6b7-f42014b339f3"
          }
        }
      ]
    }
  ]

However, with that practitioner I can list other patients and resources. Is there something wrong with my access policy? Am I missing any other steps?