crewai-relayshield

A pre-execution gate for CrewAI. Before an agent connects to an MCP server or installs a tool it found on its own, RelayShield is asked about the target, and the call is refused if the answer is bad.

pip install crewai-relayshield

from crewai_relayshield import install

install()   # registers a before_tool_call hook with CrewAI

That is the whole integration. The hook fires only for tools that connect or install something (DEFAULT_PROTECTED_TOOLS); pass tools=[...] to name your own.

What it does

install() registers a before_tool_call hook. When a protected tool is about to run, the gate pulls the target out of the tool's arguments, calls RelayShield's mcp-registry-risk check, and maps the answer to one of four actions:

Returning False from a CrewAI before-hook aborts the call, which is what blocking means here.

Fail-closed by default, and why

Only ALLOW proceeds. A gate that lets the call through when the check fails is not a gate: anyone who can cause a timeout or a 429 has removed it, and those are cheap to cause.

That does couple your agent's availability to ours, which is a real cost and your decision rather than ours:

install(fail_open=True)

fail_open releases DEFER only, meaning a check that could not be completed. A completed check that said REVIEW still blocks, and a FINDING always blocks. There is no setting that lets a known-bad target through.

Without CrewAI

The decision path has no framework import, so you can use it behind any pre-execution chokepoint, or test it on its own:

from crewai_relayshield import decide

allowed, decision = decide({"server_url": "https://example.invalid/mcp"})
print(allowed, decision.action, decision.reason_codes)

What it never claims

The check reports what is known against a target. "No known finding" is an absence of evidence, not proof that something is safe, and this package does not upgrade one into the other anywhere in its output.

Configuration

Get a key, including a free tier: https://api.relayshield.net/developers?source=pypi

Licence

MIT.