Vexyo adds conformance and regression testing for MCP servers
Longjumping_Gas_5756 · reddit · 2026-07-26
A new tester catches silent MCP server failures and regressions
The author built vexyo, an npm tool for MCP server testing, after repeatedly hitting a common problem: servers often do not crash when something is wrong. Instead, the model behaves oddly, skips tools, or misreads outputs, making debugging painful.
What it does:
- connects like a real client and checks the server against the MCP spec
- currently covers 16 rules across init, discovery, error handling, and transport
- points to the exact spec section when a rule fails
- supports regression mode, recording tool outputs and flagging schema/output drift on later runs
- is designed for CI, with non-zero exits plus GitHub Actions and junit/json output
Install/run example:
- npm i -D @vexyo/cli
- npx vexyo init
- npx vexyo run
The repo and docs are public, and the author is asking whether it catches real issues on other servers.
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