# Custom MCP not available to agent **URL:** \ **Category:** Bug Reports\ **Tags:** mcp, plugins\ **Created:** [May 15, 2026, 4:22pm UTC](https://forum.cursor.com/t/custom-mcp-not-available-to-agent/160764 "2026-05-15T16:22:34Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Jessandro\_Benicio](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/jessandro_benicio/32/108726_2.png) [@Jessandro\_Benicio](https://forum.cursor.com/u/Jessandro_Benicio)\ **Post date:** [May 15, 2026, 4:22pm UTC](https://forum.cursor.com/t/custom-mcp-not-available-to-agent/160764/1 "2026-05-15T16:22:35Z")
### Where does the bug appear (feature/product)? Cursor IDE ### Describe the Bug When I add an MCP server by editing the mcp.json file, it isn’t available to the agent. However, if I add it through the Marketplace, it works fine. ### Steps to Reproduce When I manually add an MCP server by editing the mcp.json file, it is not available to the Agent. However, when I add it through the Marketplace, it works perfectly. It seems like the manual configuration isn’t triggering a refresh for the Agent’s toolset. ### Expected Behavior The Agent should automatically detect and load the MCP server defined in mcp.json. However, as shown in the attached screenshot, the ‘Stitch’ MCP is not appearing or available for the Agent to use. ### Screenshots / Screen Recordings ![Screenshot 2026-05-15 at 13.08.39.png](https://us1.discourse-cdn.com/cursor1/original/3X/8/e/8e5308df9b1062ec880bbbe3ec7870c6bbe62248.png) ### Operating System MacOS Linux ### Version Information IDE: Version: 3.4.20 (Universal) VSCode Version: 1.105.1 Commit: 0cf8b06883f54e26bb4f0fb8647c9500ccb43310 Date: 2026-05-15T02:26:10.351Z Layout: editor Build Type: Stable Release Track: Default Electron: 39.8.1 Chromium: 142.0.7444.265 Node.js: 22.22.1 V8: 14.2.231.22-electron.0 OS: Darwin arm64 25.3.0 ### Does this stop you from using Cursor No - Cursor works, but with this issue ---
**Author:** ![deanrie](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/deanrie/32/1263_2.png) [@deanrie](https://forum.cursor.com/u/deanrie)\ **Post date:** [May 15, 2026, 5:01pm UTC](https://forum.cursor.com/t/custom-mcp-not-available-to-agent/160764/5 "2026-05-15T17:01:18Z")
Hey, thanks for the report. I can see the screenshot. Stitch is in `mcp.json`, but the agent isn’t picking it up. This looks like a couple of known patterns, so let’s narrow it down. Can you confirm: 1. In Cursor Settings → Tools & MCP, does Stitch show up? If yes, is it enabled, and is the tool count greater than 0 or is it 0? 2. If you open a new agent chat after Stitch shows as connected in Settings, do the tools appear? 3. Which `mcp.json` did you edit, the global one `~/.cursor/mcp.json` or the project one `/.cursor/mcp.json`? 4. Open Output → MCP Logs or Cursor Logs via the Command Palette and look for lines with `McpProcess`, `ipcReady`, `Stitch`, `0 tools`. If you find anything relevant, paste it here. 5. Does this reproduce on both OSes macOS and Linux, or only on one? A couple similar threads just in case, maybe a workaround there helps: - [MCP tools only available to Agent after manually toggling server off/on (even when already enabled)](https://forum.cursor.com/t/mcp-tools-only-available-to-agent-after-manually-toggling-server-off-on-even-when-already-enabled/152859) - [MCP Server Connected (Green Dot) and Tools Discovered in Logs, but "0 tools" in UI and Agent](https://forum.cursor.com/t/mcp-server-connected-green-dot-and-tools-discovered-in-logs-but-0-tools-in-ui-and-agent/160620) Once I have the logs and answers above, it’ll be clearer where to dig next. ---
**Author:** ![Jessandro\_Benicio](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/jessandro_benicio/32/108726_2.png) [@Jessandro\_Benicio](https://forum.cursor.com/u/Jessandro_Benicio)\ **Post date:** [May 15, 2026, 6:29pm UTC](https://forum.cursor.com/t/custom-mcp-not-available-to-agent/160764/6 "2026-05-15T18:29:18Z")
1 - Stitch show up, but the UI displays “0 tools, 0 prompts, 0 resources”. My issue the same of this - [https://forum.cursor.com/t/mcp-server-connected-green-dot-and-tools-discovered-in-logs-but-0-tools-in-ui-and-agent/160620](https://forum.cursor.com/t/mcp-server-connected-green-dot-and-tools-discovered-in-logs-but-0-tools-in-ui-and-agent/160620) 2 - No. I tried opening a new Agent chat, reloading the window, and completely restarting Cursor, but the tools still do not appear. 3 - I tried with both the global `~/.cursor/mcp.json` and the project-level `.cursor/mcp.json` file. 4 - I could not find any logs containing `McpProcess`, `ipcReady`, `Stitch`, or `0 tools`. Below are the only logs that appeared: > MCP: stitch > > 2026-05-15 15:13:29.309 [info] [V2] Handling CreateClient action > > 2026-05-15 15:13:29.309 [info] [V2 FSM] connection:connect\_start: conn=idle,auth=unknown → conn=connecting,auth=unknown > > 2026-05-15 15:13:30.247 [info] MCP OAuth provider initialized > > 2026-05-15 15:13:30.955 [info] MCP HTTP exchange completed > > 2026-05-15 15:13:31.671 [info] MCP HTTP exchange completed > > 2026-05-15 15:13:31.671 [info] Successfully connected to streamableHttp server > > 2026-05-15 15:13:31.671 [info] [V2 FSM] connection:connect\_success: conn=connecting,auth=unknown → conn=connected,auth=unknown > > 2026-05-15 15:13:31.671 [info] CreateClient completed, connected: true, statusType: connected > > 2026-05-15 15:13:32.512 [warning] MCP HTTP exchange completed > > 2026-05-15 15:13:32.671 [info] MCP HTTP exchange completed > > MCP OAuth > 2026-05-15 15:13:29.322 [info] [MCPService] State transition: user-stitch none → initializing > > 2026-05-15 15:13:31.673 [info] [MCPService] State transition: user-stitch initializing → connected > > MCP Allowlist > 2026-05-15 12:51:53.873 [info] [MCPService] createClient: identifier=“user-stitch”, serverName=“stitch” > > 2026-05-15 12:51:53.873 [info] [MCPService] createClient: identifier=“user-next-devtools”, serverName=“next-devtools” > > 2026-05-15 13:02:32.738 [info] [MCPService] createClient: identifier=“user-context7”, serverName=“context7” > > 2026-05-15 13:02:32.739 [info] [MCPService] createClient: identifier=“user-stitch”, serverName=“stitch” > > 2026-05-15 13:02:35.463 [info] [MCPService] createClient: identifier=“user-stitch”, serverName=“stitch” > > 2026-05-15 13:02:53.391 [info] [MCPService] createClient: identifier=“user-context7”, serverName=“context7” > > 2026-05-15 13:02:53.391 [info] [MCPService] createClient: identifier=“user-stitch”, serverName=“stitch” > > 2026-05-15 13:02:56.268 [info] [MCPService] createClient: identifier=“user-stitch”, serverName=“stitch” > > 2026-05-15 14:58:35.497 [info] [MCPService] createClient: identifier=“user-stitch”, serverName=“stitch” > > 2026-05-15 15:12:56.872 [info] [MCPService] createClient: identifier=“user-stitch”, serverName=“stitch” > > 2026-05-15 15:12:59.769 [info] [MCPService] createClient: identifier=“user-next-devtools”, serverName=“next-devtools” > > 2026-05-15 15:13:29.306 [info] [MCPService] createClient: identifier=“user-stitch”, serverName=“stitch” > > MPC Logs > Empty 5 - Both, I test it on my MacOS and Linux.Yes, I have confirmed this on both. I tested it on my macOS and Linux machines, and the issue occurs on both systems. ---
**Author:** ![deanrie](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/deanrie/32/1263_2.png) [@deanrie](https://forum.cursor.com/u/deanrie)\ **Post date:** [May 20, 2026, 6:30pm UTC](https://forum.cursor.com/t/custom-mcp-not-available-to-agent/160764/7 "2026-05-20T18:30:05Z")
Thanks for the detailed logs and for confirming the symptom matches thread 160620. Yep, it’s the same bug. Quick summary: Stitch returns a huge `tools/list` response, around 287 KB, because each tool includes a duplicated `outputSchema` with hundreds of font enum values in `DesignTheme`. Cursor has an internal payload size limit, and when it’s exceeded the whole tools list gets silently dropped. That’s why the server shows as connected in Settings, but you see 0 tools. Connecting via Marketplace can behave differently for Stitch due to a different transport or schema variant, which explains the difference. There’s a working workaround in the same thread, the solution by @And: [MCP Server Connected (Green Dot) and Tools Discovered in Logs, but "0 tools" in UI and Agent - #10 by And](https://forum.cursor.com/t/mcp-server-connected-green-dot-and-tools-discovered-in-logs-but-0-tools-in-ui-and-agent/160620/10) It’s a Node stdio proxy that strips `outputSchema` from the `tools/list` response and shrinks the payload to about 41 KB. After that, the tools show up correctly in the UI and in the agent. The `mcp.json` config is included there too. On our side this is a bug. Even if there’s an internal limit, Cursor should show an error or warning in MCP Output, not silently drop the tools list. I’ve reported it internally, no ETA for a fix yet. ---
**Author:** ![system](https://sea3.discourse-cdn.com/cursor1/user_avatar/forum.cursor.com/system/32/99069_2.png) [@system](https://forum.cursor.com/u/system)\ **Post date:** [June 19, 2026, 6:30pm UTC](https://forum.cursor.com/t/custom-mcp-not-available-to-agent/160764/8 "2026-06-19T18:30:17Z")
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