Hello everyone,
I am running into a strict schema validation issue when trying to use the official Roblox Studio MCP server with the API. It seems to happen across all models on the platform.
The Issue: Whenever a model attempts to parse the tool schemas provided by the Roblox Studio MCP server, the request immediately fails with an HTTP 400 Bad Request (INVALID_ARGUMENT).
The backend seems to reject the schema because it strictly expects the enum property to be applied only to STRING types. It fails specifically on the materialPattern and baseMaterial properties coming from the Roblox MCP tools.
Steps to Reproduce:
-
Connect the official Roblox Studio MCP server to the environment.
-
Initialize a session with any model.
-
Prompt the model to use the Roblox MCP tools.
-
The connection drops immediately with the schema validation error.
Error Logs / TraceDetails:
Plaintext
Trajectory ID: 3612b566-84fe-4f1f-b7c5-2a2645
Error: HTTP 400 Bad Request
Sherlog:
TraceID: 0x70ce683343a0
Headers: {"Alt-Svc":["h3=\":443\"; ma=2592000,h3-29=\":443\"; ma=2592000"],"Content-Length":["355"],"Content-Type":["text/event-stream"],"Date":["Thu, 02 Apr 2026 11:57:46 GMT"],"Server":["ESF"],"Server-Timing":["gfet4t7; dur=318"],"Vary":["Origin","X-Origin","Referer"],"X-Cloudaicompanion-Trace-Id":["70ce683343a0b7e3"],"X-Content-Type-Options":["nosniff"],"X-Frame-Options":["SAMEORIGIN"],"X-Xss-Protection":["0"]}
{
"error": {
"code": 400,
"message": "* GenerateContentRequest.tools[8].function_declarations[0].parameters.properties[materialPattern].enum: only allowed for STRING type\n* GenerateContentRequest.tools[8].function_declarations[0].parameters.properties[baseMaterial].enum: only allowed for STRING type\n",
"status": "INVALID_ARGUMENT"
}
}
Relevant Info: Official Roblox MCP Documentation: https://create.roblox.com/docs/studio/mcp
Is there a known workaround for bypassing this strict schema validation, or is a fix planned for the backend to gracefully handle non-string enums in MCP tool declarations? Any help would be appreciated!
