FAST Skill

Single entrypoint for the FAST SDK ecosystem.

Install

npx skills add fastxyz/fast-skill

Example Requests

• "Check my FAST testnet balance and send SET to another fast1... address"
• "Bridge USDC from Arbitrum Sepolia into Fast"
• "Use the FAST x402 packages to protect an Express API route"

Do Not Use For

• generic EVM wallet code that does not touch FAST
• arbitrary EVM to EVM bridging presented as one SDK call
• unrelated HTTP 402 questions, payment compliance research, or non-FAST API monetization stacks

Package Map

• @fastxyz/sdk: Fast network wallet setup, balances, sends, signing, token lookup, low-level claim submission
• @fastxyz/allset-sdk: bridge flows between Fast and supported EVM routes
• @fastxyz/x402-client: pay 402-protected APIs
• @fastxyz/x402-server: return 402 requirements and protect routes
• @fastxyz/x402-facilitator: verify and settle x402 payments

If an umbrella x402 package is introduced later, treat it as a wrapper. The current source-of-truth API surface is still the role-specific client, server, and facilitator packages.

Start Here

Read references/capabilities.md first when the request involves multiple packages or unclear support.

Then route by task:

• Fast wallet, balance, send, token info, signatures: references/fast-sdk.md
• Bridge between Fast and EVM: references/allset-sdk.md
• Pay for a protected API: references/x402-client.md
• Add payments to an API: references/x402-server.md
• Run verification or settlement infrastructure: references/x402-facilitator.md

Load a flow playbook when the user asks for an end-to-end scenario:

• Fast to Fast transfer: flows/fast-to-fast-payment.md
• EVM to Fast deposit: flows/evm-to-fast-deposit.md
• Fast to EVM withdraw: flows/fast-to-evm-withdraw.md
• Chain to chain via Fast: flows/chain-to-chain-via-fast.md
• Pay an x402 API: flows/x402-pay-an-api.md
• Protect an x402 API: flows/x402-protect-an-api.md

Routing Rules

1. Choose the smallest package that fits

• Do not default to multiple FAST packages if one package solves the task.
• Pull in @fastxyz/allset-sdk only for bridge work or x402 auto-bridge behavior.
• Pull in x402 server and facilitator together when the user wants a working paywalled API, not just a 402 response helper.

2. Default to testnets unless the user explicitly asks for mainnet

• @fastxyz/sdk defaults to testnet.
• @fastxyz/allset-sdk currently exposes testnet-oriented bridge routes.
• x402 packages list both testnet and mainnet-style networks, but do not move a user to mainnet silently.

3. Treat support limits as code-level constraints

• If a route or token is not in the shipped SDK config, say so clearly before writing code.
• Do not claim AllSet supports arbitrary EVM to EVM bridging in one call. Cross-chain EVM flows are composed from two legs through Fast.
• Do not claim x402 auto-bridge works on every EVM network; check the current bridge helper and capability matrix.

4. Respect irreversible operations

• Fast sends are irreversible.
• Never overwrite ~/.fast/keys/.
• Bridge and settlement operations can move funds or consume gas. Confirm addresses and network choice before final code.

Common Issues

• If the request only says x402 or 402, confirm it is specifically about the FAST @fastxyz/* packages before routing here.
• If the user asks for unsupported routes or token mappings, stop and cite the shipped constraint from references/capabilities.md instead of approximating a solution.
• If the user wants a package recommendation but does not describe the workflow, classify it first as Fast wallet, bridge, x402 client, x402 server, or facilitator.

Working Pattern

1. Classify the request: Fast payment, bridge, x402 client, x402 server, or facilitator.
2. Read the matching reference file.
3. If the task is scenario-based, read the matching flow file too.
4. Implement against the package API that actually exists in code today.
5. Call out unsupported routes instead of papering over them.