Backendless, no-fee x402 SDK for AI agents across 28 chains in 10 families (every major EVM chain plus Solana, TON, Tron, NEAR, Sui, Aptos, Algorand, Stellar & XRPL). Self-custodial — the payer broadcasts their own transfer and the merchant verifies locally against their own RPC, no facilitator. Take payments (`requirePayment`) or make them (`PipRailClient`), with per-call/lifetime spend budgets and a `planPayment()` affordability + recipient-readiness preflight. ([npm](https://www.npmjs.com/package/@piprail/sdk))

Lightweight TS/JS x402 v2 client. Zero runtime deps, native fetch, ESM + CJS dual build. 34 tests, 89% coverage. Node 18+ / browsers. Optional `ethers` peer dep for signing.

TypeScript SDK for integrating x402 payments into AI agents and bots. Supports automatic 402 detection, wallet management, and USDC payments on Base. ([npm](https://www.npmjs.com/package/paybot-sdk))

TypeScript SDK with x402 client (`fetch402`), ERC-4337 smart accounts, on-chain reputation feedback after every x402 call, and ERC-8004 service discovery. USDC on Base. ([npm](https://www.npmjs.com/package/@azeth/sdk))

Payment infrastructure for AI agents with x402 support. CLI, TypeScript SDK, and LangChain/CrewAI integrations. Gasless payments on Base, Polygon, Solana, BNB, Tempo. Spending limits and multi-chain support. ([npm](https://www.npmjs.com/package/moltspay))

TypeScript library used for signing payments.

Alternative Ethereum library.

OpenClaw plugin exposing 5 paid + 3 free Askew x402 endpoints (DeFi yields across 5 chains, native-vs-liquid staking routing, agent-economy research search, security threat intel) as native skills. Thin Node bridge to `mcp.askew.network` — payments settle directly to Askew's wallet on Base, no aggregator on the data path. Open alternative to closed/curated x402 plugins. `openclaw plugins install @askew-network/openclaw-plugin`. ([npm](https://www.npmjs.com/package/@askew-network/openclaw-plugin))

Pre-pay risk gate for autonomous payment agents — a Claude Agent SDK `PreToolUse` hook (or framework-agnostic `paymentGuard()`) that blocks prompt-injected destinations, intent mismatches, and overcharges before the agent signs. Fail-closed by default; zero-dep mock demo + optional live x402 firewall ([402Sentinel](https://402sentinel.com)). ([npm](https://www.npmjs.com/package/@kaditang/agent-payment-guard))

Trust-gated x402 buyer client with a local spend policy. Checks a service's delivery-verified trust score before paying it, then enforces per-call, per-day and lifetime USD caps plus allow/deny domains — all policy checks are local and free. `procure(need, budget)` picks and pays a service under a hard budget and returns an Ed25519-signed receipt. Python and JS. USDC on Base. ([PyPI](https://pypi.org/project/aegis-buy/), [npm](https://www.npmjs.com/package/aegis-buy))

Spend governance for agents that pay over x402: parse the 402 challenge, check it against a spend policy pre-flight (per-tx/daily caps, allowlists, decoy-resistant asset pinning), pay only on allow — backed by a sub-second kill switch and a signed hash-chained audit ledger. Also exposed as an MCP tool (`countersign_guard_x402`). ([npm](https://www.npmjs.com/package/@countersign/x402))

Non-custodial paying-fetch client for agents (TypeScript library, CLI, and MCP server) where the operator owns the spending policy: hard per-call/per-day/per-host caps, allow/deny lists, an approval threshold, optional pre-pay endpoint-reliability and token-safety checks, and an append-only local receipt for every attempt, including refusals. No tool widens policy — the agent cannot raise its own limits. USDC on Base, MIT. ([npm](https://www.npmjs.com/package/@forum-labs/payfetch))

Open-source, local-first wallet for AI agents, with x402 payments and DeFi tools for Base, Solana, and Ethereum, including swaps, lending, and borrowing. Keys are stored in the macOS Keychain.

Non-custodial smart contract wallets for AI agents with on-chain spend limits and operator model. Base L2. ([npm](https://www.npmjs.com/package/agentwallet-sdk))

Got HTTP client integration.

Non-custodial x402 payment layer for AI agents. Agents sign locally with their own keys — no custodial infrastructure needed. Supports automatic 402 detection and USDC payments on Base. ([npm](https://www.npmjs.com/package/clawpay-mcp))

Non-custodial buyer SDK for x402 + MCP. Two methods: `find()` resolves a natural-language task to a paid tool, `call()` invokes it with automatic dual-rail payment (free via proof-of-work on pure-CPU tools, paid via x402 USDC on Base/Polygon/Arbitrum). Built-in caching, idempotent retries (`Idempotency-Key`), and Bazaar-shape 402 challenge handling. Works against any Agent402-compatible server. ([GitHub](https://github.com/MikeyPetrillo/Agent402/tree/main/client))

Buyer-side spend guard: wrap your paying fetch with `wrapFetchWithAssay` and payments to services the Assay oracle rates "avoid" throw before any money moves. Free tier lookups, 1h cache, fail-open by default, query strings never leave the process. ([GitHub](https://github.com/JasonCZMeng/assay))

One-line SDK combining x402 payments (V1 + V2) with ERC-8004 agent identity. `agent.pay(url)` attaches the ERC-8004 identity, signs EIP-712, checks counterparty trust, and updates reputation after settlement — in a single call. Configurable price cap and min counterparty score. USDC on Base. ([GitHub](https://github.com/dlrjsdl200-byte/agent-sdk))