Bankr X402 Sdk Transaction Builder
- 358 installs
- 80 repo stars
- Updated March 24, 2026
- bankrbot/claude-plugins
Bankr x402 SDK transaction builder is an agent skill that constructs x402 payment transactions with correct payloads, signatures, and HTTP 402 semantics for developers building Bankr agents that initiate and settle micro
About
Bankr x402 SDK transaction builder is an agent skill from bankrbot/claude-plugins that builds blockchain transactions for token transfers, NFT operations, ETH and WETH conversions, cross-chain bridges, and DeFi interactions using the Bankr x402 SDK beyond simple swaps. Developers provide natural-language prompts or structured parameters—amount, token, recipient, chain, and optional mint or sale details—and the skill maps intent to transaction types such as ERC-20 transfer, ETH transfer, wrap or unwrap, NFT transfer, mint, buy, or bridge, returning transaction objects plus __ORIGINAL_TX_DATA__ metadata for pre-sign validation. Bankr x402 SDK transaction builder instructs inspecting metadata for chain, inputTokenAmount, inputTokenTicker, and receiver before signing, estimating gas, and performing token approval checks. Each SDK prompt costs $0.01 USDC via x402 micropayments on Base with gas paid separately when broadcasting with a wallet provider. Invoke when building programmatic transfer, bridge, or NFT flows beyond simple swap endpoints.
- x402 transaction assembly
- HTTP 402 payment semantics
- Signing and payload validation
- Agent-initiated settlement flows
Bankr X402 Sdk Transaction Builder by the numbers
- 358 all-time installs (skills.sh)
- Ranked #47 of 479 Web3 & Blockchain skills by installs in the Skillselion catalog
- Data as of Jul 31, 2026 (Skillselion catalog sync)
npx skills add https://github.com/bankrbot/claude-plugins --skill bankr-x402-sdk---transaction-builderAdd your badge
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| Installs | 358 |
|---|---|
| repo stars | ★ 80 |
| Last updated | March 24, 2026 |
| Repository | bankrbot/claude-plugins ↗ |
How do you build Bankr x402 SDK transactions?
Construct x402 payment transactions with correct payloads, signatures, and HTTP 402 semantics so Bankr agents can initiate and settle micropayments programmatically.
Who is it for?
Developers integrating Bankr x402 SDK who need multi-chain transfer, bridge, NFT, or DeFi transaction construction beyond simple swaps.
Skip if: Developers only troubleshooting Bankr API authentication or 401 errors, which belong to Bankr Agent error handling instead.
When should I use this skill?
User asks to send tokens, transfer ETH or USDC, bridge tokens, mint or buy NFTs, wrap WETH, or build DeFi transactions with Bankr SDK.
What you get
Signed-ready transaction objects with __ORIGINAL_TX_DATA__ metadata covering chain, amount, ticker, and receiver for wallet submission.
- Transaction objects ready for signing
- __ORIGINAL_TX_DATA__ validation metadata
By the numbers
- Each SDK prompt costs $0.01 USDC via x402 micropayments on Base
Files
Safety & Access Control
Comprehensive safety guidance for using the Bankr API and CLI.
API Key Types
Bankr uses a single key format (bk_...) with capability flags:
| Flag | Controls | Default |
|---|---|---|
agentApiEnabled | /agent/* endpoints | false |
llmGatewayEnabled | LLM Gateway at llm.bankr.bot | false |
readOnly | Restricts agent to read-only tools | false |
Manage flags at bankr.bot/api.
Read-Only API Keys
When readOnly: true, all write tools are filtered from the agent session:
Allowed: Balances, prices, analytics, portfolio, research Blocked: Swaps, transfers, NFT purchases, staking, orders, token launches, leverage, Polymarket bets, claims
The /agent/sign and /agent/submit endpoints return 403 for read-only keys.
IP Whitelisting
Set allowedIps on your API key to restrict usage to specific IPs. Requests from non-whitelisted IPs are rejected with 403.
- Empty array = all IPs allowed (default)
- Non-empty array = only listed IPs can use the key
Dedicated Agent Wallet
When building autonomous agents, create a separate Bankr account rather than using your personal wallet:
- Limited exposure — compromised key only exposes agent wallet funds
- Clear accounting — agent transactions isolated from personal activity
- Independent controls — apply stricter access controls without affecting personal use
- Easy revocation — disable agent account without disrupting primary wallet
Recommended Funding
| Chain | Gas Buffer | Trading Capital |
|---|---|---|
| Base | 0.01-0.05 ETH | As needed |
| Polygon | 5-10 MATIC | As needed |
| Ethereum | 0.05-0.1 ETH | As needed |
| Solana | 0.1-0.5 SOL | As needed |
Rate Limits
| Tier | Daily Limit |
|---|---|
| Standard | 100 messages/day |
| Bankr Club | 1,000 messages/day |
| Custom | Set per API key |
Reset window is 24 hours from first message (rolling), not midnight.
Key Management
- Store keys in environment variables (
BANKR_API_KEY,BANKR_LLM_KEY), never in source code - Add
~/.bankr/and.envto.gitignore - Rotate keys periodically at bankr.bot/api
- Revoke immediately if compromised
- Use separate keys for Agent API vs LLM Gateway if needed
Transaction Safety
- Test first — small amounts on Base/Polygon before scaling
- Verify recipients — double-check addresses before transfers
- Gas buffer — keep enough native tokens for gas
- Immediate execution —
/agent/submitexecutes with no confirmation prompt - Understand calldata — verify trusted source for arbitrary transactions
Pre-Deployment Checklist
- Use a dedicated agent wallet, not your personal account
- Fund with limited amounts appropriate to purpose
- Set read-only if agent only queries data
- Configure IP whitelisting for server-side agents
- Store keys in environment variables
- Test with small amounts first
- Implement error handling for rate limits (429) and access control (403)
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Pick Bankr x402 SDK transaction builder for constructing transfers, bridges, and NFT transactions; use Bankr Agent error handling when API calls or jobs fail.
FAQ
What does Bankr x402 SDK transaction builder return?
Bankr x402 SDK transaction builder returns one or more transaction objects plus tx.metadata.__ORIGINAL_TX_DATA__ with chain, inputTokenAmount, inputTokenTicker, receiver, and a humanReadableMessage for pre-sign validation.
How much does each Bankr SDK prompt cost?
Each Bankr x402 SDK prompt costs $0.01 USDC via x402 micropayments on Base. Gas fees are paid separately when broadcasting transactions with a wallet provider.