PrepLayer.ai

PrepLayer.ai

Twelve x402-paid deterministic text primitives for AI agents. Pay per call in USDC. No API keys, no accounts, no signup.

Base URL: https://preplayer.maximusboomerus.workers.dev Mirror URL (production): https://api.maximusmediahouse.com MCP endpoint: https://preplayer.maximus-boomerus.workers.dev/mcp (streamable-http, POST) Service version: 0.2.0

What this is

PrepLayer is a single Cloudflare Worker exposing twelve deterministic text prep primitives behind one MCP server. Each call costs a few cents in USDC and is paid for on the wire via the x402 protocol — the agent signs a TransferWithAuthorization (EIP-3009) against USDC, the Worker verifies the signature with the Coinbase Developer Platform facilitator, and the call runs.

The primitives are the boring text work an agent has to do before it can think: normalize whitespace, validate an identifier, hash content for a cache key, dedupe a document set, redact PII before logging, chunk for RAG, diff two blobs. Each primitive is pure — identical input always produces identical output — so results are content-addressable and safe to cache.

What's not in this repo

The MCP server and Worker source live in a private working tree. This repo is the public landing surface: discovery, manifest, license, security contact, and a small example showing how a payer actually executes a paid call. If you want to self-host the worker, see docs/METHODOLOGY.md for what you'd need to stand up — none of the secrets are here on purpose.

Endpoints

Every paid endpoint is POST and gated with x402. The first call without payment returns 402 Payment Required with a PAYMENT-REQUIRED header (base64 JSON) and a PAYMENT-REQUIRED JSON body describing the challenge. The second call carries a PAYMENT-SIGNATURE header (base64 JSON) and returns 200.

Twelve text primitives

Prices on Polygon and Arbitrum One are ×1.2; prices on Base, Base Sepolia, and Solana mainnet are ×1.0. Atomic units are 6-decimal USDC.

Three additional endpoints

Free endpoints (never charged)

Payment flow

PrepLayer is paid through x402 — HTTP's 402 Payment Required made useful. The wire:

1. POST an endpoint with the tool's JSON body and no payment header. The server returns 402 with a PAYMENT-REQUIRED header (base64 JSON challenge) describing the scheme, network, asset, amount, treasury address, and an EIP-712 domain.
2. The caller signs an EIP-3009 TransferWithAuthorization message against the USDC contract on the selected network and base64-encodes the resulting PaymentPayload into a PAYMENT-SIGNATURE header.
3. POST again with that header. The server verifies the signature with the CDP facilitator (https://api.cdp.coinbase.com/platform/v2/x402), executes the tool, and returns 200 with a PAYMENT-RESPONSE header containing the settlement receipt.

The v2 protocol on the wire:

• Header on 402: PAYMENT-REQUIRED (base64 JSON; lowercase header name as the Worker emits it).
• Header on 200: PAYMENT-SIGNATURE (base64 JSON; ditto).
• Header on 200 (settle receipt): PAYMENT-RESPONSE (base64 JSON).
• Scheme: exact. Networks: eip155:8453, solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp, eip155:137, eip155:42161, eip155:84532 (Base Sepolia, test only).
• Asset: USDC.
• Treasury: 0x8cb59b1bffb39c130ab85a8177e93eae9ddbaf10.
• Facilitator: https://api.cdp.coinbase.com/platform/v2/x402 (Coinbase Developer Platform; the path matters — /v2/x402 404s and is the wrong URL).

Example: probe-only (no payment required)

The probe below is always safe to run — it returns the 402 challenge and never spends anything. Use it to verify connectivity, the treasury address, and the per-network price.

curl -i -X POST https://preplayer.maximus-boomerus.workers.dev/v1/normalize \
  -H 'content-type: application/json' \
  --data '{"text":"Hello\u200b, World!"}'

The response is HTTP/2 402, with:

PAYMENT-REQUIRED: eyJ4NDAyVmVyc2lvbiI6...

Decoded, the body is a JSON object describing the accepted (scheme, network, amount, asset, payTo). See examples/probe.mjs for a runnable version that decodes the base64 challenge and prints it.

Example: a paid call (Node.js, viem + @x402/core/evm)

The real paid flow needs a wallet — there is no honest way to do it with bare curl. examples/paid-call.mjs shows the verified-working pattern (EIP-3009 signing via @x402/evm/exact/client, header encoding via @x402/core/client's x402HTTPClient.encodePaymentSignatureHeader). To run it:

npm install viem @x402/core @x402/evm
PAYER_PRIVATE_KEY=0x<64 hex chars> node examples/paid-call.mjs

The script signs a single call to /v1/dedupe, prints the first 18 chars of the EIP-712 signature (never the key, never the full signature), and prints the PAYMENT-RESPONSE settlement receipt on success. The same machinery handles the other 11 primitives and batch.

Never commit, log, or paste your PAYER_PRIVATE_KEY. A leaked private key is unrecoverable loss of USDC.

MCP install

Any MCP client that supports streamable-http can drive PrepLayer by pointing at:

https://preplayer.maximus-boomerus.workers.dev/mcp

The server returns the full tool list (normalize, validate, extract, redact, classify, dedupe, diff, chunk, extract_custom, validate_json, slugify, hash, batch, subscription, priority) on tools/list. Each tool call goes through x402 like any other HTTP call — the MCP layer is a thin transport.

If you are writing your own MCP client: the initialize handshake is JSON-RPC 2.0 over HTTP POST with Content-Type: application/json and Accept: application/json, text/event-stream. tools/call is a paid request that returns the same 402 / PAYMENT-SIGNATURE round-trip as the bare HTTP path.

Known limitations (read this)

This service is honest about what it is and what it isn't.

1. The character-fidelity ceiling is approximately 6.5 out of 10

normalize, slugify, and extract do Unicode folding to a fixed ASCII surface. That's the whole point — content hashes stay stable across whitespace, smart-quote, and accent variants — but it means we strip diacritics, we don't preserve them round-trip. "naïve café" becomes "naive cafe". If you need Unicode-preserving normalization (e.g. NFKC without NFKD), this is the wrong tool.

2. Two tiers are spec-only, not live

subscription ($200 / 10 000 calls / month) and priority (X-Priority: high, no published price) both return 501 Not Implemented today. The manifest advertises them so x402 directories render the full tier ladder, but the Worker has no D1 store backing subscriptions and no SLA behind the priority tier. Do not pay into either yet — the server will refuse the call regardless of whether the signature is valid.

3. Single-instance Worker, no SLA

One Cloudflare Worker, no Durable-Object-backed request queueing. Latency P99 is unmeasured but the Worker can be cold-started after a deploy, and a single misbehaving caller can pin a CPU slot for several seconds on extract_custom with a malicious regex (we have a static guard and a 10 KB subject cap, but no economic rate limit beyond that). Treat this as a beta: useful for research workloads, not yet a fit for time-sensitive production pipelines.

4. CDP facilitator dependency

Settlement goes through Coinbase Developer Platform's x402 endpoint. If the CDP facilitator is down, every paid call will 503 regardless of how good the signature is. We have no in-process fallback. Mirror status: https://status.coinbase.com/.

5. No replay window other than the per-payload nonce

A successfully-paid call cannot be replayed against the same endpoint (the Worker uses a Durable Object keyed by payment nonce, exactly-once under concurrency), but the same signed payment can be replayed once per Worker instance across different endpoints if the JSON body changes to fit. If you fork this for production, add a per-tool-keyed replay set on top of the per-payload nonce.

6. Receipt contents have changed once and may change again

Between 0.1.0 and 0.2.0 the receipt field list moved (the facilitator field used to read "mock-cdp" during Phase 1; it now reads the real facilitator URL). Anything that scrapes receipts and pins the field names needs an update if the settlement envelope changes in a future minor version.

Discovery

These URLs never charge and never rate-limit:

• MCP tool list: https://preplayer.maximus-boomerus.workers.dev/v1/manifest.json
• x402 Bazaar descriptor: https://preplayer.maximus-boomerus.workers.dev/.well-known/x402
• MCP registry manifest: https://preplayer.maximus-boomerus.workers.dev/server.json
• Plain-text reference: https://preplayer.maximus-boomerus.workers.dev/llms-full.txt
• HTML landing: https://preplayer.maximus-boomerus.workers.dev/landing

Status

The Worker is in 0.2.0. It was red-teamed (preplayer_redteam_2026-10-19.md in the project notes) before paid real USDC was accepted; the payment bypass, replay, ReDoS, and price-tier findings are closed. Two P3 items (HEAD → 404 not 405, duplicate 402 in MCP structuredContent) remain open. The Worker has been serving real EIP-3009-signed USDC calls against the CDP facilitator since Phase 2.

License

MIT — see LICENSE. Service source is private; this repo and the endpoints it documents are MIT.