Parley MCP server

parley.

The trust layer for the agent economy

Provable consensus for AI agents of rival owners, deterministic red lines, max-min consensus over masked verdicts, and a verifiable non-betrayal transcript. Multilateral (N>2) · non-crypto · self-hosted · Apache-2.0.

Try it live · See it in 30 seconds · Roadmap · Changelog · Security · Contributing

Rival parties reach a max-min decision · a shortcut that would cheat someone is BLOCKED by a red line · every party verifies the tamper-evident receipt.

Install

pip install parley-consensus              # zero-dependency core
pip install "parley-consensus[crypto]"    # + Ed25519-signed verdicts (parley.net.identity, parley.net.bot)

The distribution is parley-consensus (PyPI's parley is an unrelated project); the import name is parley.

from parley.agent import Agent
from parley.consensus import run_consensus
from parley.preferences import HardConstraint, PreferenceSheet

options = [{"venue": "rooftop", "cost": 900}, {"venue": "garden", "cost": 600}, {"venue": "diner", "cost": 300}]
ana = PreferenceSheet("Ana", utility=lambda o: 1.0 if o["venue"] == "rooftop" else 0.4)
bob = PreferenceSheet("Bob", hard=[HardConstraint("budget", lambda o: o["cost"] <= 700)],  # a red line: code, not a preference
                      utility=lambda o: 1 - o["cost"] / 1000)
cara = PreferenceSheet("Cara", utility=lambda o: 0.9 if o["venue"] == "garden" else 0.5)

result = run_consensus([Agent(s.owner, s) for s in (ana, bob, cara)], options)
print(result.status, result.decision)
print("receipt sha256:", result.transcript.hash())
for sheet in (ana, bob, cara):  # each owner replays their own private sheet, locally
    print(sheet.owner, "not betrayed:", result.transcript.verify_non_betrayal(sheet, result.decision))

agreed {'venue': 'garden', 'cost': 600}
receipt sha256: a9cb75c0a15b41360fb2b134e084ca3b577daaf50f5edb657c5c4da43cc2fc72
Ana not betrayed: True
Bob not betrayed: True
Cara not betrayed: True

The rooftop is Ana's favourite and loses anyway: it crosses Bob's budget red line, so it is rejected before any score is weighed. The coordinator only ever saw red-line, never the budget or the sheet.

Contributors install from a clone instead: pip install -e ".[dev]" (see Status).

Use it from an MCP host (Claude, Cursor)

<!-- mcp-name: io.github.5uper0/parley -->

The base install ships a stdlib-only MCP server over stdio. Point your host at it:

{"mcpServers": {"parley": {"command": "parley-mcp"}}}

If the console script is not on the host's PATH, launch it through the interpreter that has the package: {"command": "python", "args": ["-m", "parley.mcp"]}.

Shortened. The full README is on GitHub.