agent-gate

An MCP server that lets an AI agent gate its own work before it claims "done" — deterministic checks → independent refute-first review → a tamper-evident honest receipt.

Agents that grade their own homework ship slop. agent-gate turns that discipline into tools an agent must actually pass: a fail-closed checklist and an append-only, hash-chained receipts ledger. It's Fleet Mode — my agent-orchestration doctrine — made into a runnable tool. Receipts over hype, enforced by the data structures.

agent: "done!"  →  verify_gate(evidence)  →  { passed: false, blocking: ["independent_refute_review", "no_secrets"] }

Why

The expensive failures in agent systems are the silent ones: a model update degrades output, a change quietly breaks a workflow, an agent declares success while the work is wrong. The fix isn't a smarter model — it's a gate the agent can't talk its way past:

• Fail-closed. A check counts as satisfied only if it's explicitly true. Missing proof is not proof. (Mirrors a promotion gate, not a vibe check.)

• Tamper-evident receipts. Every decision is recorded as (decision, metric, value, verdict) linked into a sha256 chain. Edit or delete any past receipt and verify_chain() returns false. The honest log is enforced by the structure, not by good intentions.

• Human-gated by default. "Any irreversible/outward act got human approval" is a required check — agents draft, humans approve.

Tools (over MCP)

The default ship gate encodes Fleet Mode: deterministic_checks_pass, independent_refute_review, no_secrets, human_gated_if_irreversible, honest_receipt_logged.

Install & wire into an MCP client

pip install -e .          # or: pip install agent-gate

Add it to your MCP client (Claude Desktop / Claude Code) config:

{
  "mcpServers": {
    "agent-gate": { "command": "python", "args": ["-m", "agent_gate.server"] }
  }
}

Now your agent can call verify_gate(...) before it tells you it's finished — and you get a tamper-evident trail of what it decided. Receipts persist to ~/.agent-gate/receipts.jsonl (override with AGENT_GATE_LEDGER).

Use it directly (no MCP client needed)

from agent_gate.gate import DEFAULT_SHIP_GATE
from agent_gate.ledger import Ledger

res = DEFAULT_SHIP_GATE.evaluate({
    "deterministic_checks_pass": True,
    "independent_refute_review": True,
    "no_secrets": True,
    "human_gated_if_irreversible": True,
    # honest_receipt_logged missing  →  fail-closed
})
print(res.passed, res.blocking)   # False ['honest_receipt_logged']

led = Ledger("receipts.jsonl")
led.append(decision="ship v0.1", metric="tests", value="17", verdict="shipped")
print(led.verify_chain())         # True  (until someone edits the log)

Design

• Tested, dependency-free core. agent_gate/gate.py (fail-closed checklist) and agent_gate/ledger.py (hash-chained receipts) are pure stdlib — fast to read, fast to trust. agent_gate/server.py is a thin MCP adapter over them.

• 17 tests, CI on Python 3.11–3.13. The MCP tools are tested by calling them, not just importing.

Tests

pip install -e ".[dev]" && python -m pytest -q

About

Built by Jeff Otterson (Jott2121). agent-gate operationalizes the gating discipline from bow (an autonomous all-Claude chief-of-staff agent) and the Fleet Mode doctrine. MIT licensed.