Roblox Studio MCP server: tool responses appear truncated to structured summary, full results not rendered

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When using the official Roblox Studio MCP server (shipped by Roblox, enabled via Studio's "Enable Studio as MCP server" toggle), tool responses for script_grep, search_game_tree, inspect_instance, and script_search reach Claude Code as one-line summaries instead of the documented structured payload. Roblox Studio's own built-in Assistant, talking to the same MCP server, receives full results — so the plugin is sending the data; it's being lost on the Claude Code side.

What Should Happen?

Tool responses should include the full payload documented in each tool's schema — e.g. script_grep should return a results array of file paths and matched lines (capped at 50), search_game_tree should return an array of instance objects, inspect_instance should return properties/attributes/children. Whatever the Roblox plugin emits in the text-content portion of the MCP response should be visible to the model.

Error Messages/Logs

No errors thrown. Responses are silently truncated. Examples received in Claude Code:

- script_grep "<query>" → {"count":5,"noMatch":false,"query":"<query>"}
- search_game_tree {keywords: "<x>"} → {"count":3,"keywords":"<x>"}
- inspect_instance "StarterPlayer.StarterPlayerScripts" → {"instanceName":"StarterPlayerScripts"}
- script_search "<keywords>" → {"count":2,"keywords":"<keywords>"}

The same script_grep query in Studio's in-Studio Assistant returns the full list of script paths plus context.

Steps to Reproduce

1. Open Roblox Studio with any place that has scripts in it.
2. In Studio: Assistant Settings → MCP Servers → toggle "Enable Studio as MCP server" on.
3. Register the server with Claude Code using the command Studio's Quick Connect generates:
4. claude mcp add --transport stdio Roblox_Studio cmd.exe /c "%LOCALAPPDATA%\Roblox\mcp.bat"
5. In Claude Code, ask the model to run script_grep for any string known to exist in the place.
6. Observe the response is {count, noMatch, query} only — no results array.
7. For comparison, ask Studio's built-in Assistant the same question — full results returned.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

Unknown.

Claude Code Version

2.1.121.

Platform

Other

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

script_read on an exact path works correctly. list_roblox_studios and set_active_studio also work correctly. So the channel is healthy — only tools that return larger structured/array payloads are affected.

Hypothesis: MCP tool responses can carry both structuredContent (typed JSON) and content (text blocks). The Roblox plugin likely sends the full results in the text part; Claude Code may be rendering only structuredContent for this server, dropping the actual data before it reaches the model.

/bug and /feedback both fail in this session ("/feedback is only available for local sessions on this desktop build"), which is why this is filed via GitHub.

MCP launcher path: %LOCALAPPDATA%\Roblox\mcp.bat → StudioMCP.exe shipped inside Roblox version folder 547feaebd3b44131 (binary dated 2026-04-29).