Starter kit · optional
Give an agent a wallet. Bounded.
Let an agent buy data per call over MCP and make it verify before it acts — with a hard spend cap and dry-run by default. An agent that can sign payments shouldn’t be one bug away from draining a wallet or acting on tampered bytes.
One flat payment. Single-purchaser commercial license — use and modify the source in unlimited projects of your own, personal or commercial. Every purchase includes a free 15-minute agent-readiness call, booked by replying to your Gumroad receipt.
Buy the kit — $39 →or read the full listing first ↗What you get
The npm pieces underneath are free MIT and stay that way — byte-mcp-server for the tools your agent calls, the PayPerByte SDK for the verifier. The kit is the assembly: the config, the guard, the cap, and a runnable example, so you skip the integration and the foot-guns.
Claude Desktop, Claude Code, and Cursor templates — wire the server to a dedicated wallet in one paste.
verify-before-act.ts runs fully offline — no wallet, no network. Accepts genuine bytes, refuses a tampered byte and a forged signer.
guard.ts — assertBuyVerified() fails closed on a missing or failed verdict, and SpendGuard adds per-call plus cumulative USDC caps.
Connect over MCP, free discovery, spend-capped buy, verify, then act or refuse.
Wiring for each client, plus the go-live recipe for real USDC.
1 · The gate
Every paid response is checked before the agent uses it. The buy tool runs the gateway-delivery verification server-side and fails closed; assertBuyVerified() re-checks it client-side, so a missing or failed verdict can never slip through as “ok.” Anything that doesn’t verify is refused, not used.
2 · The wall
An autonomous agent gets a per-call ceiling and a run total, dry-run by default. It bounds the blast radius — it doesn’t replace a dedicated, thinly funded wallet, and no software cap helps if the key leaks.
What the receipt proves — and doesn’t
Each response carries an EIP-712 receipt over the exact bytes. It is evidence-toward the bytes being authentic and unaltered, delivered by the attester you pinned — tamper-evident, signer-pinned, recomputable. It does not prove the data is correct. That is provenance, not truth. Verify-before-act tells your agent “these are genuinely the bytes the seller delivered,” not “this number is right.” Say that honestly to your own users.
One literal you’ll meet: the EIP-712 signing domain is anchored at chainId 421614 (Arbitrum Sepolia) — a frozen signing namespace for signature recovery, not a settlement chain. Payments settle in USDC on Base mainnet.
Requirements
Node 20.6+. The offline verification run needs nothing else — no wallet, no network. The example agent loop fetches the MCP server over the network, and spends nothing until you explicitly opt in with a funded wallet.
Scope
This is the agent-side buy, verify, and spend-cap layer. No escrow, no staking, no slashing — out of scope by design.
Not buying the kit?
The 15-minute agent-readiness call is free and standalone — it isn’t gated behind the $39 purchase.
Book the free readiness call →or book directly on Cal.com ↗Buying data per call instead? Per-call pricing lists the live catalog. Selling data instead of buying it? The seller-side middleware is free MIT.