Four tools over MCP stdio, so a coding assistant can ask Hound about a
project at the moment it matters rather than after:
hound_check_project the full supply-chain sweep
hound_check_package is this package known bad, before installing it
hound_check_file one file: a model, a lockfile, a manifest
hound_check_mcp_config audit the servers your assistant already trusts
READ-ONLY, permanently. There is no hound_quarantine, no hound_delete,
no way to change a setting. An agent can be persuaded by the very
repository it is inspecting — that is the threat this product exists to
detect — so a destructive MCP tool would hand the attacker exactly the
capability they were reaching for. A test asserts every tool name starts
with hound_check_ and contains none of quarantine/delete/remove/restore/
settings/set/update/install/write/exec, so the property cannot erode.
The output is written to be read twice: by the model that called the
tool, and by the human reading that model's summary. That rules out rule
identifiers and jargon — a test greps the output for both — and it rules
out ambiguity about severity. A model reading "1 warning" may well decide
to proceed, so a critical finding leads with an explicit recommendation
and names the consequence: this runs code during installation, before
any of the project's own code runs.
Clean results say what they did NOT check. "Nothing wrong" that reads as
a blanket endorsement is worse than no answer, so a clean project notes
it is not a source review, a clean name check notes it did not read the
package's contents, and a clean MCP audit still points out that every
server listed runs with your permissions and is called without asking.
The server passes its own audit, which was the point:
{ "mcpServers": { "hound": { "command": "/usr/bin/hound-mcp" } } }
No npx, so nothing is fetched at launch. No env, so no secret is handed
over. No path argument, so it is granted no directory. Hound's MCP audit
flags all three in other people's configs; a security tool that failed
its own check would have answered the only question that mattered.
Verified against the installed binary.
Protocol notes, since both are easy to get wrong and fatal:
- a notification carries no id and must never be answered; MCP sends
notifications/initialized straight after the handshake, so replying
corrupts the stream on the first exchange
- an id of 0 is still an id, and treating it as absent silently drops
the first call from any client that counts from zero
- a tool failure is a RESULT with isError, not a JSON-RPC error: the
agent should see "I could not read that path" as an answer it can act
on, not a transport fault that looks like a broken server
- nothing but protocol messages ever goes to stdout; diagnostics go to
stderr, because one stray println corrupts the session
Shipped in the .deb, and the postinstall now prints the config entry.
334 tests pass.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Hound