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MCP tools fail to load when outputSchema contains unresolved refs #26529
Description
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 #/$defs/ScreenInstance from id # failed to get tools from client
The server responds to initialize and tools/list, but OpenCode fails while validating/dereferencing the tool schema and then reports the whole MCP server as failed.
Plugins
None relevant.
OpenCode version
1.14.41
Steps to reproduce
- Configure Google Stitch as a remote MCP server.
- Run
opencode mcp list --log-level DEBUG --print-logs. - Observe that the Stitch MCP transport connects, then tool loading fails on an
outputSchema$ref.
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ERROR service=mcp key=stitch error=can't resolve reference #/$defs/ScreenInstance from id # failed to get tools from client
Operating System
macOS
Terminal
zsh
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github-actions commentedon May 9, 2026
This issue might be a duplicate of existing issues. Please check:
can't resolve reference #/$defs/ScreenInstance from id #with Google Stitch MCP, same OpenCode version 1.14.41Consider adding your information to one of those issues instead.
shiju-tectaliya commentedon May 9, 2026
stitch-mcp-auto (universal, with auto-setup & OAuth)
npx -p stitch-mcp-auto stitch-mcp-auto-setupOpenCode 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`
test(mcp): reproducer for anomalyco#26529 — outputSchema unresolved r…
fix(mcp): tolerate invalid tool output schemas