Compared to the Python SDK

Same on-chain contract, same oracle nodes. Different runtime assumptions.

The official Charli3 SDK is written in Python. It works. But if your app is on Node, Next.js, or Vercel, you have to run a second Python service next to it. charli3-js removes that step.

Both SDKs do the same on-chain work

They call the same oracle nodes, trust the same keys, and build a Round 2 tx the same on-chain contract accepts. The chain does not care which SDK you used. That is the point.

Scope. charli3-js covers ODV pull oracles (Round 1 + Round 2). The Python SDK also covers the older push oracles and some Charli3 ops tools. If you need those, keep using the Python SDK.

Same action, different code

python-sdk-config.yaml

# client.yaml that the Python SDK loads at boot
network: preprod
blockfrost:
  project_id_env: BLOCKFROST_PROJECT_ID
  base_url: https://cardano-preprod.blockfrost.io/api

wallet:
  mnemonic_env: WALLET_MNEMONIC
  account_index: 0
  address_index: 0

oracle:
  pair: ADA/USD
  address: addr_test1wq...
  policy_id: 886dcb2363e160c944e63cf544ce6f6265b22ef7c4e2478dd975078e
  tokens:
    c3cs: "43334353"
    c3ra: "43334241"
    c3as: "43334153"
    c3rt: "43335254"
  odv_validity_length_ms: 300000
  price_precision: 6

reference_script:
  utxo_reference:
    tx_id: 7a69e9d3d90826f861107e4b503c56e08c40d092416a50bad37fc89865a78cd1
    index: 0

nodes:
  - root_url: http://35.208.117.223:8001
    pub_key: ed25519_pub_1a9b...0f2c
  - root_url: http://35.208.117.223:8002
    pub_key: ed25519_pub_7c44...e81d
  # ...four more nodes

The practical differences

	Python SDK	charli3-js
Runtime	Python 3.10+, virtualenv, pycardano	Node 20+, same process as your app
Config	client.yaml (40+ lines, edited by hand)	Preset ships with each release; update with npm update
Integration	60 to 80 lines of setup code	3 lines per action
Next.js fit	Separate Python service running next to your app	Drop it into an API route, works on Vercel
Keys	Wallet seed in env, handled by the SDK	Any Lucid wallet: seed, browser wallet (Lace), HD key
Time to first tx	About half a day (setup, YAML, deploy)	Under 10 minutes
On-chain result	Same datum	Same datum

Why this matters for Cardano builders

Most Cardano tools (Lucid, MeshSDK, Blockfrost, Lace, Vercel templates) are JavaScript or TypeScript. Asking someone to add a Python service just to read a price is a lot. Asking them to add one npm package is not.

Fewer moving parts means:

• More oracle-backed apps get built (less setup to do)
• More Round 2 txs happen (which is how Charli3 earns)
• Fewer things break in production
• No extra server just to read one price

When to use which

Use charli3-js

You are building a web app, a Next.js API route, a Cardano wallet, a Discord bot, a CLI tool, or an AI agent that already runs on Node.

Use the Python SDK

You need push-oracle support, Charli3 ops tools, or you already run Python with pycardano.

They can work together

You can run the Python SDK for one job and charli3-js for another. They read the same on-chain data and produce the same kind of tx. Mix and match by service.