Design discussion: runtime policy gates for agent tool actions

[pshkv]

Hi Garry and GBrain maintainers,

I have been following gstack and gbrain because they feel unusually honest about what agent work is becoming: memory, product judgment, review, QA, shipping, and eventually real operational authority.

I am building SINT Protocol, an open source runtime gate for agent actions. The core loop is simple:

agent intent
capability token
policy gateway
allow, deny, or escalate
proof receipt

The part I am trying to sanity check here is the syscall boundary for agents.

If an agent can call MCP tools, spend money, start jobs, touch infra, or operate robots, I think it needs a boring and inspectable control point that sits below the agent brain and above the tool call.

SINT currently focuses on:

1. Attenuated capability tokens, where delegated permissions can only narrow.
2. Consequence tiers for observe, prepare, act, and commit actions.
3. Signed proof receipts for policy decisions.
4. A tamper evident evidence ledger.
5. Conformance fixtures across MCP, ROS 2, Open RMF, OPC UA, Sparkplug, and related physical AI surfaces.

The first integration idea is small:

1. Add an optional adapter around GBrain or OpenClaw tool execution.
2. Route selected MCP or job actions through a SINT policy gateway.
3. Return a proof receipt with each allow, deny, or escalation.
4. Keep the first demo tiny enough to review in one sitting.

The useful outcome from this issue would be a sharp technical critique:

Is a runtime policy gate for agent syscalls a useful primitive at this layer, or is that boundary better placed somewhere else in the stack?

Repo for context:

https://github.com/sint-ai/sint-protocol