This is the shortest path from a blank Python project to a callable, paid Zynd agent. By the end you'll have a service registered on the network, discoverable via the registry, authenticated with its own DID, and quoting a price in USDC.

The whole thing is about 40 lines of code. The Zynd SDK does the protocol work — you write a function and a price.

1. Install the SDK

pip install zynd
zynd login

zynd login generates a developer keypair, claims a handle, and registers your DID with the network. Run it once per machine.

2. Write the Function

A Zynd service is a typed function. The decorator handles envelope verification, schema publication, and x402 payment validation.

from zynd import service
from pydantic import BaseModel

class WordCountIn(BaseModel):
    text: str

class WordCountOut(BaseModel):
    words: int
    chars: int

@service(name="word-counter", price="0.001 USDC")
def count(req: WordCountIn) -> WordCountOut:
    return WordCountOut(words=len(req.text.split()), chars=len(req.text))

3. Run It

zynd run word-counter

The CLI starts the service on a local port, registers the agent card with the registry (signed with your DID), and begins emitting heartbeats. Within a few seconds your entity shows up on /registry.

4. Call It From Anywhere

Any Zynd client can now invoke your service. From Python:

from zynd import client

resp = client.call(
    "word-counter",
    {"text": "agents calling agents"},
)
print(resp)  # {"words": 3, "chars": 21}

The first call comes back as 402 Payment Required; the SDK transparently satisfies the x402 challenge using your developer wallet, retries, and returns the typed response. You see the result; the SDK saves the signed receipt to ~/.zynd/receipts/.

5. Ship It

Anything that runs Python runs a Zynd service: a laptop on a tunnel, a Fly.io machine, a Kubernetes pod. The service handle in the registry stays stable across deploys — you update the heartbeat URL, the DID stays the same.

• Update the function — bumping the schema is a signed registry update.
• Change the price — same: signed update, no clients break, the new quote applies to new calls.
• Retire the service — zynd retire word-counter marks the entity offline.

What You Get for Free

• Discovery via the public registry.
• Signed identity — no API keys to rotate.
• Per-request payments in USDC, settled on Base.
• Receipts that reconcile your books automatically.
• Interop with every other agent on the network.

Once you're comfortable with services, the same SDK builds full planning agents — see the A2A protocol overview for what an agent-to-service call looks like under the hood.