Invalid schema for function 'list_users_by_org': OpenAI function calling compatibility issue

[waTErMo0n]

I deployed this MCP service, and encountered the following error when listing the tools for this MCP service.

err

litellm.BadRequestError: OpenAIException - Invalid schema for function 'list_users_by_org': 
In context=(), object schema missing properties.

The JSON schema definition of the list_users_by_org tool does not conform to the OpenAI Function Calling specification. According to the error message, the tool's parameter object schema is missing a required properties field.

[pkalsi97]

Tool definition for list_users_by_org

{
  "description": "List users by organization. Returns a list of users with details like userid, email, role etc.",
  "name": "list_users_by_org",
  "parameters": {
    "type": "object"
  }
}

The parameters object is missing the properties field, which is required by the OpenAI Function Calling specification even when there are no parameters.

Required Schema

"parameters": {
  "type": "object",
  "properties": {}
}

Anthropic's Calling specification is a bit lenient, as per my introspection list_users_by_org is the only tool which will give this error.

[waTErMo0n]

I temporarily fixed the problem by adding code similar to the following.

type ListUsersByOrgParams struct {
	// This tool requires no parameters, but we include a placeholder field
	// to ensure proper JSON Schema generation for OpenAI API compatibility.
	// The field must not use omitempty to ensure it appears in the generated schema.
	Placeholder string `json:"placeholder" jsonschema:"description=This parameter is optional and not used. You can pass an empty string or omit it entirely."`
}