What is Capxul?
A typed SDK for Accounts, payments, Permissions, and Organizations.
Capxul is a financial-operations platform. The Core SDK is the primary developer interface; the React SDK projects that client into a provider, queries, and mutations. Both keep custody substrate outside normal application vocabulary.
import { createCapxulClient } from "@capxul/sdk";
const created = await createCapxulClient({ publishableKey });
if (!created.ok) throw created.error;
const account = await created.value.accounts.read();
if (!account.ok) throw account.error;
console.log(account.value.balance);Learn the Core SDK
Create a client, authenticate, and read an Account without React.
Integrate React
Add the React SDK projection after you understand the Core SDK boundary.
Look up exact contracts
Check packed exports, method bundles, results, and explicit scaffolds.
Check what is available
See which operations work, which are limited, and which are not available yet.
The surface is Stripe-shaped
Money is just money. A developer using the SDK never has to know the words "Safe", "UserOp", "wei", or a chain id to move money. Crypto is the substrate, never the vocabulary — any custody term appearing in the consumer-facing surface is treated as a defect (a leak). You work with:
- Money — a currency, a decimal value, and a precision. Never wei.
- Accounts — a person's or org's pot of money, identified by an opaque id. Never an address.
- Payments — money sent to a validated recipient, a handle, an email, or a saved payee. Never a raw chain address.
Read the mental model and the money & accounts glossary for the full vocabulary.
Two products, one platform
- Capxul App is the customer-facing financial-operations product.
- Capxul SDK (these docs) is the platform layer it is built on — the same primitives are published for other product teams, external developers, and agents to build with.
Agent-native by design
The SDK is built with the expectation that agents participate in both building and operating products. Every capability is a safe, structured primitive an agent can compose: the MCP server exposes financial operations as tools, every docs page is available as raw markdown, and llms.txt indexes the whole site for machine readers.
Packages
| Package | What it is |
|---|---|
@capxul/sdk | The Core SDK — production client plus its ./testing entry. |
@capxul/sdk-react | React bindings — production provider/hooks plus its ./testing entry. |
@capxul/mcp | The Capxul MCP server — financial operations as agent tools. |
@capxul/observability | Shared product and engineering telemetry catalog, profiles, and transports. |
@capxul/sandbox | Sandbox CLI — create test publishable keys and send testnet faucet funds. |
Published packages use one synchronized stable release train. Pin exact matching versions and check Capability status before depending on an operation in production.
Where to start
- Using TypeScript? Start with the SDK tutorial.
- Building a React UI? Continue with the React provider tutorial, then use the hook catalog as reference.
- Wondering what's real today? Read Capability status.
- Contributing to the platform? Start at Contributing.
- Building with agents? See the agent surface.