fix(mcp): don't fail connection for resource-only servers#14223
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aasmall wants to merge 2 commits intoanomalyco:devfrom
Open
fix(mcp): don't fail connection for resource-only servers#14223aasmall wants to merge 2 commits intoanomalyco:devfrom
aasmall wants to merge 2 commits intoanomalyco:devfrom
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Remove the listTools() gate from create() that closed MCP clients when tool listing failed. Servers exposing only resources (no tools capability) were incorrectly marked as failed. Tool discovery is already deferred to MCP.tools() which handles per-server listing lazily. Fixes anomalyco#11841
Tests that MCP servers exposing only resources (no tools capability) are not rejected during connection. Covers resource-only, empty capability, and mixed capability scenarios.
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Pull request overview
This PR fixes a bug where MCP servers that only expose resources (no tools capability) were incorrectly failing to connect. The issue occurred because create() was calling listTools() as a health check immediately after connection, which threw CapabilityNotSupported for resource-only servers.
Changes:
- Removed the
listTools()health check from the connection flow increate()function - Added capabilities logging to show which capabilities (tools, resources, prompts) the server supports
- Added comprehensive tests covering resource-only, empty capability, and mixed capability servers
Reviewed changes
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| File | Description |
|---|---|
| packages/opencode/src/mcp/index.ts | Removed premature listTools() health check and replaced with capabilities logging |
| packages/opencode/test/mcp/resource-only.test.ts | Added test coverage for resource-only, empty, and mixed capability MCP servers |
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Issue for this PR
Closes #11841
Type of change
What does this PR do?
After connecting,
create()callslistTools()as a health check and closes the client if it fails. Servers that only expose resources (no tools capability) get rejected because the SDK throwsCapabilityNotSupportedonlistTools(), which the.catch()swallows intoundefined, triggering the "Failed to get tools" path.The
listTools()result here was never cached or reused — tool discovery already happens lazily viaMCP.tools()when tools are actually needed. Removed the gate and replaced it with a capabilities log.How did you verify your code works?
Added 3 tests in
test/mcp/resource-only.test.tscovering resource-only, empty capability, and mixed capability servers. All connect successfully. Verified the tests fail against the old code (listTools()throws on the mock client). Full test suite passes (1095 pass, 0 fail). Typecheck clean.Screenshots / recordings
N/A — no UI changes.
Checklist