MCP tools fail to load when outputSchema contains unresolved refs

[nicolascancino]

Description

OpenCode can mark an MCP server as failed even when the server is reachable and tools/list responds, if one tool's outputSchema contains a reference the MCP SDK cannot resolve.

Observed with Google Stitch MCP on OpenCode 1.14.41:

ERROR service=mcp key=stitch error=can't resolve reference #/$defs/ScreenInstance from id # failed to get tools from client

The server responds to initialize and tools/list, but OpenCode fails while validating/dereferencing the tool schema and then reports the whole MCP server as failed.

Plugins

None relevant.

OpenCode version

1.14.41

Steps to reproduce

1. Configure Google Stitch as a remote MCP server.
2. Run opencode mcp list --log-level DEBUG --print-logs.
3. Observe that the Stitch MCP transport connects, then tool loading fails on an outputSchema $ref.

Screenshot and/or share link

ERROR service=mcp key=stitch error=can't resolve reference #/$defs/ScreenInstance from id # failed to get tools from client

Operating System

macOS

Terminal

zsh

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• MCP: failed to get tools from Stitch - can't resolve reference #/$defs/ScreenInstance #26260: Same error can't resolve reference #/$defs/ScreenInstance from id # with Google Stitch MCP, same OpenCode version 1.14.41
• MCP: Google Stitch remote MCP fails with 'Failed to get tools' despite working via curl #26382: Google Stitch remote MCP failing to get tools with the same underlying issue, also on 1.14.41

Consider adding your information to one of those issues instead.

[shiju-tectaliya]

stitch-mcp-auto (universal, with auto-setup & OAuth)
npx -p stitch-mcp-auto stitch-mcp-auto-setup

OpenCode config:
`{
"$schema": "https://opencode.ai/config.json",
"mcp": {
"stitch": {
"type": "local",
"command": ["npx", "-y", "stitch-mcp-auto"],
"enabled": true,
"timeout": 120000,
"environment": {
"STITCH_API_KEY": "{env:STITCH_API_KEY}"
}
}
}
}

Prompt: Diagnose stitch mcp server`