Is openapi 3.0.x supported actually ?

[thedevd]

Hi @jlowin , Is openapi 3.0.x really supported with fastmcp 2.11.x version. As I just tried openapi 3.0.x api specification and I am still seeing input schema validation error.

Error- when calling tool
Input validation error: None is not of type 'string'

Schema example I am trying - (Note - I have verified my openapi 3.0.x schema using swagger online editor, and there things are ok)

{
  "openapi": "3.0.0",
  "info": {
      "title": "UAC",
      "description": "Manage users, roles etc",
      "version": "1"
  },
  "paths": {
  .....
  .....
   "/api/v1/users": {
          "get": {
              "operationId": "v1_users_list",
              "responses": {
                  "200": {
                      "description": "OK",
                      "content": {
                          "*/*": {
                              "schema": {
                                  "$ref": "#/components/schemas/UserSerializer"
                              }
                          }
                      }
                  },
                  "400": {
                      "description": "Bad Request"
                  },
                  "401": {
                      "description": "Authentication credentials were not provided"
                  },
                  "403": {
                      "description": "Forbidden"
                  }
              },
              "parameters": [
                  {
                      "name": "uuid",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "role",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "usergroup",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "tenant",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "current_logged_in",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "is_active",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "is_internal",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "is_locked",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "is_staff",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "email",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "email__startswith",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "email__contains",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "first_name",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "first_name__startswith",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "first_name__contains",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "last_name",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "last_name__startswith",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "last_name__contains",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "username",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "username__startswith",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "username__contains",
                      "required": false,
                      "in": "query",
                      "description": "",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "search",
                      "required": false,
                      "in": "query",
                      "description": "A search term.",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "ordering",
                      "required": false,
                      "in": "query",
                      "description": "Which field to use when ordering the results.",
                      "schema": {
                          "type": "string"
                      }
                  },
                  {
                      "name": "page",
                      "required": false,
                      "in": "query",
                      "description": "A page number within the paginated result set.",
                      "schema": {
                          "type": "integer"
                      }
                  },
                  {
                      "name": "limit",
                      "required": false,
                      "in": "query",
                      "description": "Number of results to return per page.",
                      "schema": {
                          "type": "integer"
                      }
                  }
              ],
              "description": "List of users.\n\nCustom Filter current_logged_in can be used to get currently logged in users,\nGET api/v1/users?current_logged_in=True",
              "summary": "List of users.",
              "tags": [
                  "v1_users"
              ]
          },

[jlowin]

That error means your API is returning null for a field that the schema says isn’t nullable, and is being evaluated in the low level SDK so we can’t improve the error message. If you can confirm that the schema says nullable and FastMCP is incorrectly changing to non-nullable, then we can address. We have a new test suite for this specific issue. Otherwise this is an issue with the API itself which we’ve also seen.

[thedevd]

I would say, my API schema says that input params are nullable as required is false for all of them. And also my API works fine without passing any params if tried directly using swagger

And forgot to mention that, with last version 2.10.6, I did not observe input schema validation error for same API which I am trying.
See this works-

But with 2.11.0, input schema validation is reported -

Anyway, how to verify if FastMCP is changing them to non-nullable or keeping them nullable when parsing the schema ?