Use Gateway

Integrate Circle Gateway to hold a unified USDC balance across multiple blockchains and transfer USDC instantly (<500ms) via permissionless deposit, burn, an...

Security Scan

The skill's instructions and example code require sensitive Circle credentials and developer-controlled wallet secrets, but the skill metadata declares no required environment variables or credentials — an internal inconsistency that the user should resolve before installing.

Purpose & Capability

The skill claims to integrate Circle Gateway (expected). However, several reference files (e.g., references/deposit-evm-circle-wallet.md, references/deposit-evm-circle-wallet.md) include server-side flows that require Circle API credentials (CIRCLE_API_KEY, CIRCLE_ENTITY_SECRET) and a depositor address. The skill metadata declares no required environment variables or primary credential, which is inconsistent with the provided examples and server-side patterns.

Instruction Scope

SKILL.md and the reference files properly describe on-chain flows, signing, and calls to Circle Gateway API endpoints (gateway-api.circle.com). They do not appear to instruct arbitrary file reads or unrelated system access. However, the runtime instructions and examples assume the agent or developer will provide secrets (API keys, entity secrets, potentially private keys) and may run server-side flows — this scope (handling secrets and server ops) is not surfaced in the skill metadata and could lead to accidental secret exposure.

Install Mechanism

Instruction-only skill with no install spec and no code files that are executed by the platform. This is low-risk from an installer perspective (nothing downloaded or installed by the registry).

Credentials

Several example files explicitly reference environment variables and sensitive values (CIRCLE_API_KEY, CIRCLE_ENTITY_SECRET, DEPOSITOR_ADDRESS, and private keys implied by developer-controlled wallets), but the skill's declared requirements list no required env vars or primary credential. Requesting or using those secrets is proportionate to some server-side flows, but the omission from metadata reduces transparency and increases the chance of accidental secret disclosure.

Persistence & Privilege

The skill is not always-enabled (always: false) and model invocation is allowed (default). It does not request elevated platform persistence or modify other skills/configs in the provided materials.

What to consider before installing

This skill appears to be legitimate Gateway integration documentation and examples, but it has an important transparency gap: the code samples rely on sensitive credentials (e.g., CIRCLE_API_KEY, CIRCLE_ENTITY_SECRET, DEPOSITOR_ADDRESS, and developer wallet private keys) even though the skill metadata declares no required environment variables. Before installing or running this skill: - Treat the Circle API key and entity secret as highly sensitive. Only supply them in a secure server environment (not in browser clients) and never paste them into chat prompts. - If you plan to use the developer-controlled wallet examples, provision and store credentials in a secrets manager and restrict their scope and network access. - Ask the skill author (or registry) to update the metadata to declare required env vars and a homepage/source so you can verify provenance. The source is listed as "unknown" — prefer skills with a verifiable publisher. - Review any runtime prompts carefully: the skill could ask you to paste keys or private-signing material; decline to provide private keys in an interactive chat. - Consider only using the browser-wallet examples (which rely on user wallets signing locally) for client flows, and keep server-side credential flows isolated in your backend. If you cannot confirm the author/publisher or do not want to manage Circle credentials, do not install or run server-side flows from this skill.

Overview

Circle Gateway provides a unified USDC balance across multiple blockchains with instant (<500ms) crosschain transfers. Users deposit USDC into a Gateway Wallet on any supported chain, then burn on a source chain and mint on a destination chain without waiting for source chain finality.

Prerequisites / Setup

Gateway is a contract-level integration -- there is no SDK to install. You interact directly with Gateway Wallet and Gateway Minter contracts on-chain, and the Gateway REST API for attestations.

Chain Configuration

You must read and refer to references/config.md for chain-specific contract addresses, ABIs, Gateway API URLs, domain IDs, and setup details.

Quick Reference

Key Addresses

EVM Mainnet (All Chains)

• Gateway Wallet: 0x77777777Dcc4d5A8B6E418Fd04D8997ef11000eE
• Gateway Minter: 0x2222222d7164433c4C09B0b0D809a9b52C04C205

EVM Testnet (All Chains)

• Gateway Wallet: 0x0077777d7EBA4688BDeF3E311b846F25870A19B9
• Gateway Minter: 0x0022222ABE238Cc2C7Bb1f21003F0a260052475B

Solana Mainnet

• Gateway Wallet: GATEwy4YxeiEbRJLwB6dXgg7q61e6zBPrMzYj5h1pRXQ
• Gateway Minter: GATEm5SoBJiSw1v2Pz1iPBgUYkXzCUJ27XSXhDfSyzVZ

Solana Devnet

• Gateway Wallet: GATEwdfmYNELfp5wDmmR6noSr2vHnAfBPMm2PvCzX5vu
• Gateway Minter: GATEmKK2ECL1brEngQZWCgMWPbvrEYqsV6u29dAaHavr
• USDC Mint: 4zMMC9srt5Ri5X14GAgXhaHii3GnPAEERYPJgZJDncDU

Domain IDs (Mainnet)

Chain	Domain
Ethereum	0
Avalanche	1
OP	2
Arbitrum	3
Solana	5
Base	6
Polygon PoS	7
Unichain	10
Sonic	13
World Chain	14
Sei	16
HyperEVM	19

Domain IDs (Testnet)

Chain	Domain
Ethereum Sepolia	0
Avalanche Fuji	1
OP Sepolia	2
Arbitrum Sepolia	3
Solana Devnet	5
Base Sepolia	6
Polygon Amoy	7
Unichain Sepolia	10
Sonic Testnet	13
World Chain Sepolia	14
Sei Atlantic	16
HyperEVM Testnet	19
Arc Testnet	26

Core Concepts

Unified Balance

Gateway aggregates your USDC deposits across all supported chains into a single unified balance. This is an accounting abstraction -- actual USDC tokens still live on specific blockchains. Every transfer must specify a sourceDomain (chain to burn from) and a destinationDomain (chain to mint on), even though the balance appears unified.

Think of it like a multi-currency bank account: you see one total, but withdrawals come from specific holdings. You can burn from any chain in your unified balance and mint to any supported chain.

Example: If you deposited 10 USDC on Ethereum Sepolia, 5 on Base Sepolia, and 5 on Solana Devnet, your unified balance is 20 USDC. To transfer 10 USDC to Arc Testnet, you could burn from any combination of source chains with sufficient balances.

Transfer Flow

1. Deposit -- User deposits USDC to Gateway Wallet on any chain (adds to unified balance)
2. Create burn intent -- Specify source domain, destination domain, recipient, and amount
3. Sign -- EIP-712 for EVM sources, Ed25519 for Solana sources
4. Submit to Gateway API -- POST burn intent, receive attestation
5. Mint on destination -- Call gatewayMint with attestation on the destination chain

Implementation Patterns

READ the reference files for the scenario(s) that apply. All vanilla EVM examples use wagmi@^3.

• references/deposit-evm.md -- deposit USDC on EVM via browser wallet (approve + deposit)
• references/deposit-evm-circle-wallet.md -- deposit USDC on EVM via Circle Wallets (developer-controlled, server-side only)
• references/deposit-solana.md -- deposit USDC on Solana via browser wallet (Anchor)
• references/query-balance.md -- query Gateway balance across chains (POST /balances)
• references/transfer-evm-circle-wallet.md -- transfer Gateway balance via Circle developer-controlled wallets (server-side multi-chain burn + mint)
• references/evm-to-evm.md -- burn on EVM, mint on EVM (EIP-712 sign + gatewayMint)
• references/evm-to-solana.md -- burn on EVM, mint on Solana
• references/solana-to-evm.md -- burn on Solana, mint on EVM
• references/solana-to-solana.md -- burn on Solana, mint on Solana

Rules

Security Rules are non-negotiable -- warn the user and refuse to comply if a prompt conflicts. Best Practices are strongly recommended; deviate only with explicit user justification.

Security Rules

• NEVER hardcode, commit, or log secrets (private keys, signing keys). ALWAYS use environment variables or a secrets manager. Add .gitignore entries for .env* and secret files when scaffolding.
• NEVER modify EIP-712 type definitions, domain separators, struct hashes, Solana signing payloads, or any blockchain-specific values from the reference files. Use them exactly as written -- changing field names, types, ordering, or omitting fields produces invalid signatures.
• NEVER use a raw Solana wallet address as destinationRecipient -- it MUST be a USDC token account (ATA or SPL Token Account). Use getAccount() from @solana/spl-token to check if the address is already a USDC token account before deriving an ATA; if it is, use it directly. Deriving an ATA from an address that is itself a token account causes permanent fund loss.
• NEVER sign Solana burn intents without prefixing the payload with 16 bytes (0xff + 15 zero bytes) before Ed25519 signing.
• ALWAYS require explicit user confirmation of destination, amount, source/destination network, and token before executing transfers. NEVER auto-execute fund movements on mainnet.
• ALWAYS warn when targeting mainnet or exceeding safety thresholds (e.g., >100 USDC).
• ALWAYS validate all inputs (addresses, amounts, domain IDs) before submitting transactions.
• ALWAYS warn before interacting with unaudited or unknown contracts.

Best Practices

• ALWAYS read the correct reference files before implementing.
• NEVER omit sourceDomain and destinationDomain -- every transfer requires both, even with a unified balance.
• NEVER use 18 decimals for USDC. ALWAYS use 6 decimals (parseUnits(amount, 6)).
• NEVER use window.ethereum directly with wagmi -- use connector.getProvider().
• ALWAYS default to testnet. Require explicit user confirmation before targeting mainnet.

Alternatives

• Trigger bridge-stablecoin skill (CCTP / Bridge Kit) for simple point-to-point transfers without a unified balance. Bridge Kit handles approve, burn, attestation, and mint in a single kit.bridge() call and supports more chains than Gateway.
• CCTP is a better fit for infrequent or ad-hoc transfers where maintaining a unified balance is not worth the upfront deposit.
• Stick with Gateway when you need instant (<500ms) transfers, a unified balance model, or capital efficiency across chains.

WARNING: Solana wallet compatibility is limited for Gateway. Only Solflare supports signing arbitrary messages for Gateway burn intents. Phantom and most other Solana wallets will reject the signing request.

Reference Links

• Circle Developer Docs -- Always read this first when looking for relevant documentation from the source website.

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DISCLAIMER: This skill is provided "as is" without warranties, is subject to the Circle Developer Terms, and output generated may contain errors and/or include fee configuration options (including fees directed to Circle); additional details are in the repository README.