PayPerByte MCP Server

June 24, 2026 · View on GitHub

A Model Context Protocol server that gives AI agents direct access to PayPerByte — verified, provenance-first data feeds for AI agents. Agents discover feeds, pay-per-call via x402 (settled in USDC on Base mainnet), or subscribe to on-chain streams (Arbitrum Sepolia testnet). Every paid x402 response carries an EIP-712 PayloadAttestation receipt (X-BYTE-Attestation header) the agent verifies before acting. No tokens, no API keys, no off-chain accounts.

Two rails — read this before setting PRIVATE_KEY.

x402 pay-per-call (byte_buy_data): Base mainnet (eip155:8453), REAL USDC. Paid feeds settle real money — the flagship Address Reputation Oracle is $0.05 per verdict. Use a dedicated wallet holding only what you intend to spend.

On-chain subscribe/publish/query layer (BYTE Library contracts + indexer): Arbitrum Sepolia testnet (chain 421614), MockUSDC. Mainnet for this layer is gated on an external security audit. The EIP-712 attestation signing domain stays anchored at 421614 regardless of which rail you paid on.

One PRIVATE_KEY serves both rails. Never reuse a key holding funds you can't afford to spend.

Quick start

npx -y byte-mcp-server

Wire it into your MCP client (Claude Desktop config below), then your agent can:

Discover feeds: "List the PayPerByte catalog" / "Search publishers for weather"
Buy one packet (x402, no setup): "Check this receiving address before I pay it" → $0.05 real USDC on Base mainnet, signed ALLOW/WARN/BLOCK verdict with an attestation receipt
Subscribe to a stream (testnet): "Subscribe me to the earthquakes feed" → auto-approves MockUSDC for ongoing settlement on Arbitrum Sepolia
Query a fact (testnet): "Ask the fact-oracle who won the last Lakers vs Warriors game" → on-chain signed answer with citations

The live catalog is at x402.payperbyte.io/feeds — verified, provenance-first feeds across weather, markets, code, security, and knowledge.

Verify before acting (ForeSeal)

See the whole verify-before-act loop in one command — no install, no signup, no wallet:

npx @foreseal/demo

It runs locally (no real USDC) and shows an agent ACT on genuine bytes and REFUSE four attacks — a tampered byte, a forged signature, a missing receipt, a forked signing domain — in about a second.

The same primitive ships as two packages you can drop into your own stack:

Kit — @payperbyte/sdk: the buyer verifies a receipt before acting.
Gate — @foreseal/gate: a seller stamps a verifiable receipt on any x402 endpoint.

Mode	Tool	Rail	Best for	Pricing
Buy (x402)	`byte_buy_data`	Base mainnet — real USDC	One-off needs (single snapshot or verdict for this user query)	Per-feed, quoted in the 402 challenge ($0.05 flagship; most feeds cents or less)
Subscribe	`byte_subscribe`	Arbitrum Sepolia — testnet MockUSDC	Continuous streams (every weather update, every new earthquake)	$0.003 / KB per delivery

Buy is zero-setup, pay-as-you-go, and live with real settlement; subscribe delivers every broadcast on the audit-gated testnet layer. Pick by access pattern.

Tools (15 total)

Discovery (read-only, no wallet)

Tool	Description
`byte_search_publishers`	Search publishers by topic and sort order
`byte_list_feeds`	List the active feed catalog with prices and frequencies
`byte_get_publisher`	On-chain info for one publisher (status, subscribers, messages, USDC revenue, schema)
`byte_get_network_stats`	Network-wide stats: publishers, messages, total fees settled
`byte_check_subscription`	Is `subscriber` subscribed to `publisher`?
`byte_list_my_subscriptions`	All active subscriptions for a wallet — last 7d/30d messages + USDC spend
`byte_subscription_health`	Content-drift signal for a publisher: stable / moderate / significant / unknown
`byte_get_token_balances`	USDC + ETH balances on Arbitrum Sepolia
`byte_verify_payload`	Verify-before-act. Recompute `keccak256` of the bytes your agent received and check them against the publisher's on-chain EIP-712 `PayloadAttestation` — anchor with an `expectedHash` you hold or the settlement `txHash` (which also recovers the signer and confirms it's the named publisher). If `verified: false`, the data was tampered/corrupted in transit — don't act on it

Tool	Description
`byte_subscribe`	Subscribe to a publisher's stream. Auto-bundles USDC `approve(max)` unless `skipAllowance: true` (closes a silent-payment-failure footgun where the contract's allowance-skip path delivered data with `amount=0`)
`byte_unsubscribe`	Unsubscribe — takes effect next block
`byte_register_publisher`	Register as a data publisher (schema + on-chain registration). v1 is first-party only; stake = 0
`byte_publish_data`	Publish a payload to a subscriber via DataStream (settles fee in USDC). See migration notice above re: r2

Buy on-demand (requires `PRIVATE_KEY`)

Tool	Description
`byte_buy_data`	Buy one packet from any feed via the x402 gateway — real USDC on Base mainnet. No subscription, no allowance. Signs EIP-3009 `transferWithAuthorization` against the 402 challenge; the facilitator settles on-chain. Returns the data + tx hash inline
`byte_query_fact`	Ask a slashable fact-oracle publisher a question. Signed EIP-712 request (binds query to your wallet so leaked queries can't burn your escrow); the answer is broadcast on-chain to your address with citations

Configuration

Claude Desktop

Edit ~/.config/claude/claude_desktop_config.json (Linux) or ~/Library/Application Support/Claude/claude_desktop_config.json (macOS):

{
  "mcpServers": {
    "byte-library": {
      "command": "npx",
      "args": ["-y", "byte-mcp-server"],
      "env": {
        "PRIVATE_KEY": "0x...",
        "RPC_URL": "https://sepolia-rollup.arbitrum.io/rpc",
        "INDEXER_URL": "http://localhost:8080"
      }
    }
  }
}

PRIVATE_KEY is optional — read-only tools work without it. Add it to enable subscribe, publish, buy, and query.

Claude Code

claude mcp add byte-library -- npx -y byte-mcp-server

Environment variables

Variable	Required	Default	Description
`PRIVATE_KEY`	only for write/buy/query tools	—	EOA key. Signs real Base-mainnet USDC for `byte_buy_data` and testnet txs for subscribe/publish/query — use a dedicated wallet
`RPC_URL`	no	`https://sepolia-rollup.arbitrum.io/rpc`	Arbitrum Sepolia RPC (the on-chain read/subscribe layer)
`INDEXER_URL`	no	`https://feeds.payperbyte.io`	PayPerByte indexer API
`BYTE_GATEWAY_URL`	no	`https://x402.payperbyte.io`	x402 gateway base URL (used by `byte_buy_data`)

Network

Two rails, honestly stated:

x402 payment rail (byte_buy_data): Base mainnet (eip155:8453). Paid feeds settle real USDC through the gateway at x402.payperbyte.io; each paid 200 returns an X-BYTE-Attestation EIP-712 receipt over the exact response bytes.
On-chain layer (subscriptions, broadcasts, fact-oracle escrow, indexer): Arbitrum Sepolia (chain 421614). Mainnet for the BYTE Library contracts is gated on an external security audit. The EIP-712 PayloadAttestation signing domain is anchored on 421614 regardless of the payment rail.

Contract addresses are pinned in the bundled config; the npm release ships ready-to-use defaults. No token.

Development

git clone https://github.com/0rkz/byte-mcp-server.git
cd byte-mcp-server
npm install
npm run build && npm start

License

MIT — see LICENSE.