Every tool call,
a signed receipt. A tamper-proof record of everything
your AI agent does — that anyone can check.

$ pip install aevs

# with framework adapters
$ pip install "aevs[langchain,mcp]"

$ python -c "import aevs; print(aevs.__version__)"
0.1.0

import os
import aevs
from dotenv import load_dotenv

load_dotenv()  # reads ./.env into os.environ

aevs.configure(
    api_key=os.environ["AEVS_API_KEY"],
    agent_id=os.environ["AEVS_AGENT_ID"],
)
aevs.enable()  # auto-detects langchain, mcp

# run your agent normally — every tool call is
# intercepted, HMAC-signed, and hash-chained.

for r in aevs.get_reference_ids(clear=True):
    print(r["tool_name"], "→", r["reference_id"])

import os
import aevs
from dotenv import load_dotenv
from langchain_openai import ChatOpenAI
from langchain.agents import create_agent

load_dotenv()  # reads ./.env into os.environ

aevs.configure(
    api_key=os.environ["AEVS_API_KEY"],
    agent_id=os.environ["AEVS_AGENT_ID"],
)
aevs.enable(frameworks=["langchain"])

agent = create_agent(
    model=ChatOpenAI(model="gpt-4o"),
    tools=[],  # pass your tools here
)
await agent.ainvoke({"messages": [
    ("user", "pay $142 to acme for inv 91"),
]})
aevs.flush()  # drain the local buffer before exit

# Public verify endpoint — no auth required
$ curl https://api.aevs.fetch.ai/v1/receipts/verify/<reference_id>

{
  "data": {
    "verified":      true,
    "reference_id":  "d4e5f6a7-b8c9-…",
    "receipt_id":    "7c1e2a90-3b4d-…",
    "tool_name":     "approve_payment",
    "agent_id":      "3b9a4d52-9c01-4e8f-9c11-…",
    "status":        "success",
    "input_hash":    "a1b2c3d4e5f6…",
    "output_hash":   "c4a8e2f1b9d3…",
    "in_timestamp":  "2026-04-28T10:00:00.000Z",
    "out_timestamp": "2026-04-28T10:00:00.450Z"
  }
}