a2o-ana 0.1.1

Out-of-the-box NATS-based agent-to-agent (A2A) protocol and Python client.

ana — out-of-the-box NATS agent-to-agent bus

A small Python package that gives you the boring parts of an A2A (agent-to-agent) protocol so you can focus on what your agents actually do:

• Envelope schemas — typed Query / Reply / Ack / Discovery pydantic models, one canonical wire format.
• Subject convention — <prefix>.<agent>.<verb>.<topic>, prefix configurable per fleet, parseable both directions.
• Async client (AgentBus) — thin wrapper on nats-py with publish auditing, a request/reply helper that dodges the core-NATS "no-sub means lost" gotcha, and an InboundContext that handlers can use to reply / ack without juggling state.
• CLI (ana) — listen / send / probe so shell scripts and operators don't need to import Python.

Built on top of existing NATS — bring your own cluster, anonymous or auth, core or JetStream. ana does not deploy anything.

Install

pip install a2o-ana          # PyPI distribution
# or, from source:
pip install -e .[dev]

(PyPI distribution is a2o-ana because the bare ana name was squatted in 2015. The import name stays ana — from ana import AgentBus.)

5-line bot

import asyncio
from ana import AgentBus

async def main():
    async with AgentBus("my-bot") as bus:
        await bus.query("other-bot", "what's your status?")

asyncio.run(main())

Responding bot

import asyncio
from ana import AgentBus, Query
from ana.client import InboundContext

async def handler(env, ctx: InboundContext):
    if isinstance(env, Query):
        await ctx.reply({"status": "alive", "answer": env.query})

async def main():
    async with AgentBus("my-bot") as bus:
        await bus.subscribe_to_me(handler)
        await bus.announce_discovery(role="worker")
        await asyncio.Event().wait()  # serve forever

asyncio.run(main())

Request/reply with timeout

query_and_wait subscribes to the responder's reply subject before publishing the query — so the core-NATS "publish-into-the-void" gotcha can't bite you here.

reply = await bus.query_and_wait("other-bot", "status?", timeout_s=5.0)
if reply is None:
    print("peer didn't answer in time")
else:
    print(reply.data)

CLI

# Listen for everything addressed to you
ana --identity miraku-home listen --scope self

# Send a query
ana --identity caller send query --to other-bot --query 'status?' --topic default

# Probe (send + wait for one reply)
ana --identity caller probe other-bot --query 'status?' --timeout 5

Pass --prefix myfleet.v1 to switch namespaces. Pass --nats nats://10.0.0.1:4222 to point at a non-localhost server. Pass --audit-log /var/log/ana.jsonl to record every publish.

Subject convention

Default scheme: <prefix>.<agent>.<verb>.<topic> where <topic> is optional. Verbs are query, reply, ack, discovery, policy.

cc.fleet.alice.query.status
cc.fleet.alice.reply.status
cc.fleet.alice.ack.status
cc.fleet.alice.discovery
cc.fleet.alice.policy

Pick any prefix — change SubjectScheme(prefix=...) and you're done.

Envelope schemas

All four shapes share from (sender identity), ts (ISO-8601 UTC), and type (used as the discriminator on parse). See docs/protocol.md for the full spec.

{"type": "query",     "from": "alice", "to": "bob", "query": "status?",
 "fields": ["uptime", "version"], "request_id": "ab12", "ts": "..."}

{"type": "reply",     "from": "bob", "reply_for": "cc.fleet.bob.query.status",
 "request_id": "ab12", "data": {"alive": true}, "ts": "..."}

{"type": "ack",       "from": "carol", "ack_for": "cc.fleet.carol.query.status",
 "alive": true, "ts": "..."}

{"type": "discovery", "from": "dave", "role": "worker",
 "subjects_owned": ["cc.fleet.dave.>"], "capabilities": {"gpu": "A100"}, "ts": "..."}

Core NATS gotchas

ana defaults to core NATS (no JetStream). Operational implications worth knowing up front:

• A publish made while the target has no active subscription is lost forever. There's no replay or store-and-forward.
• query_and_wait() subscribes-then-publishes, which dodges this for the request/reply pattern.
• For fire-and-forget broadcasts where loss matters, point ana at a JetStream-enabled NATS and ensure the target has a durable consumer before you publish. ana itself doesn't manage streams; do that with nats stream add.

See docs/protocol.md for envelope details and docs/nats-notes.md for deployment notes.

Examples

• examples/echo_bot.py — minimal responder.
• examples/two_bot_dialogue.py — two bots in one process exchanging query/reply.
• examples/send_query.py — one-shot probe.

Tests

pip install -e .[dev]
pytest                          # unit tests (no NATS needed)
nats-server &                   # start a local server
ANA_NATS_URL=nats://127.0.0.1:4222 pytest tests/test_bus_integration.py

License

MIT