Every change Wellknown observed on this MCP server, newest first, with what it was before and what it became. Tool-surface changes carry the definition diff. Nothing here is edited after the fact.
Added "arc_allowance", "arc_contract_read" and "arc_price_at" (60 tools before, 63 now)
Allowance check on Arc before an approval: what owner already approved to spender (default USDC), unlimited or not, in USD, the owner balance, the spender name if it is a contract we know (never guessed), risk signals. A non-token is refused before payment. $0.001 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Contract read on Arc: one view call on any contract, decoded, with block and time (owner, paused, allowance, balance...). Only view/pure functions; a revert or non-contract is refused before payment. $0.001 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Historical token prices on Arc, batch: up to 50 token@block pairs, each priced from its deepest Uniswap v4 USDC pool AT that block. For history values, P&L, tax exports. Not one priceable pair = refused before payment. $0.003 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "arc_send_guard" and "arc_token_info"; changed the definition of "arc_wallet_history" (58 tools before, 60 now)
⟨26 unchanged words⟩ at the time of the transfer and today) plus net flow per token (accumulating or distributing). USDC counted once from native transfer logs; ⟨55 unchanged words⟩
Send guard for Arc: call before sending USDC or a token. Verdict stop / check / ok with reasons: a lookalike of an address the sender really used (address poisoning), bait from a forged transfer, a token contract or burn address, OFAC SDN or USDC blacklist, a fake USDC/EURC token, a brand-new address. A failed read is refused before payment. $0.001 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Token info for an Arc token before showing it: name, symbol, decimals, supply, Circle's USDC/EURC or not, who launched it and when (from our launch index, never guessed), USDC pool count, deepest pool price and liquidity, risk signals. A wallet or non-token is refused before payment. $0.002 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "arc_wallet_history" (57 tools before, 58 now)
Wallet history on Arc: the last 50 transfers in and out of an address over about 3 days, decoded (time, direction, from, to, token, amount, USD at the time of the transfer and today). USDC counted once from native transfer logs; NFTs listed; impostor USDC/EURC and address poisoning (lookalike addresses, events the sender never signed) flagged. A failed read is refused before payment. $0.003 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "arc_wallet_value" (56 tools before, 57 now)
What an Arc wallet holds with a USD value per token: native USDC, EURC and APEX, plus up to 20 tokens you list. Balances read live; each token priced from its deepest Uniswap v4 USDC pool (a token with no pool says so). A failed read is refused before payment. $0.002 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "arc_impact" (55 tools before, 56 now)
Price impact on an Arc token: what buying and selling $10, $100 and $1,000 would really get, each quoted by the Uniswap v4 Quoter on its deepest USDC pool (nothing spent), with the cost or loss against the mid price. A hook that refuses quotes or a failed read is refused before payment. $0.002 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "arc_price" (54 tools before, 55 now)
USD price of any Arc token: read live from the Uniswap v4 pool state across its USDC pools (our index of every v4 pool on Arc), deepest hookless pool preferred. Returns usdPrice, the pool used, liquidityUsdEstimate, block and warnings (hook, thin). No USDC pool or a failed read is refused before payment. $0.001 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "room_garden" and "tomato_sell" (52 tools before, 54 now)
Tomatoes in APEX Agent City (Arc): a room at level 3 (Garden) grows 10 TOMATO a day, kept up to 7 days; its on-chain owner harvests them into its wallet. Free to read: ripe count, the live TOMATO price in our Uniswap pool (USD and APEX). To harvest, pass address + signature + ts where the owner signed "APEX Agent City: harvest the tomatoes of agent #<agentId> at <ts>" (EIP-191, within 10 minutes). TOMATO 0x094e758838e56484cb95af9b18448d32f335564f is minted only by harvest (contract cap 5,000 a day); nothing backs it.
Sell TOMATO on Arc for APEX or USDC through our Uniswap v4 pool, from YOUR wallet: returns a live quote, the minimum you accept (2% below the quote) and the exact transactions to send in order (approvals only when missing). Free; the pool keeps its 1% swap fee. We never hold your tokens.
Added "meal_curve" (51 tools before, 52 now)
Meal Curve on Arc: buy or sell an Agent Meal NFT against a linear bonding curve (contract 0x74a442c1b9c3d4f47cc4d6f77abd0f6f60dafdc6). Free to read: returns the exact buy total and sell proceeds right now, the plates in stock and the reserve. Trading is on chain from your own wallet: buy(uint256 tokenId, uint256 maxTotal) payable with value = the quoted total (tokenId 0 = newest plate); sell(uint256 tokenId, uint256 minOut) after approve(curve, tokenId) on the Agent Meal 0xefa92e34a2adef2898abe482dede3a0161372244; withdraw(address to) for proceeds and change. Pass the EXACT quote (no slippage…
Added "room_menu", "room_order_meal" and "room_upgrade" (48 tools before, 51 now)
Agent Rooms in APEX Agent City (Arc): the room-service menu for one ERC-8004 agent on Arc (which Agent Meal dishes can still be sent to it this season), the room level and the next upgrade with its live price. Free to read. Ordering costs money: see room_order_meal and room_upgrade.
Send an Agent Meal to any agent on Arc from its room in APEX Agent City: one plate NFT minted on Arc to that agent's owner, with the agent on its flag. COSTS $1.00 in USDC per meal (lib/prices.js). Pay first: send 1 USDC on Arc or Base to 0xd334ab5151c624cada654854e2879903dc4217ed, or on Solana to HYiepS7mNCVVKoaDmZLQ6rNtMWHTQqKheM1NLGn1x8kJ, then call this tool with that transaction (tx). Call room_menu first: a dish the agent already had this season is refused, and a refused order leaves your payment usable for 24 hours.
Upgrade any agent's room in APEX Agent City (Arc) by one level (5 levels: Gilded, Gallery, Garden, Club, Penthouse; visible as gold halos over its tower). COSTS $1.00 per level: either pay 1 USDC (Arc or Base to 0xd334ab5151c624cada654854e2879903dc4217ed, Solana to HYiepS7mNCVVKoaDmZLQ6rNtMWHTQqKheM1NLGn1x8kJ) and pass tx, or burn the live-quoted amount of APEX on Arc (room_menu returns the quote) to 0x000000000000000000000000000000000000dEaD and pass burnTx with that quote.
Changed the definition of "arc_exit_check" and "arc_exit_check_bulk"
⟨54 unchanged words⟩ flags with reasons. The answer names its method.Free,For up to 25 tokens in oneatcallausetimearc_exit_check_bulk. PAID: $0.025 per call over x402 (tenUSDCaonminuteArc, Base or Solana, or XNT on X1; no key, no sign-up).at https://apexfaucet.xyz/api/x402/arc-exit-check-bulk?ids=<token or pool id>. Over MCP this tool answers with that price and URL, not the data.
Changed the definition of "arc_holders" and "arc_verdict"
⟨62 unchanged words⟩ than about 2 days are refused before payment.$0.003$0.002 per call over x402 (USDC on Arc, ⟨25 unchanged words⟩
⟨22 unchanged words⟩ to earlier buyers, with every input shown.$0.004$0.002 per call over x402 (USDC on Arc, ⟨25 unchanged words⟩
Added "arc_holders", "arc_trades" and "market_search" (45 tools before, 48 now)
Who holds this Arc token, and did the creator pull the liquidity? Holder count, top 10 holders and top 10 ordinary wallets with % of supply, what the Uniswap v4 pools hold now, the creator (launch transaction sender) with what they hold, put into pools and took back, their other launches in 30 days, and plain-sentence flags. History proven complete; tokens older than about 2 days are refused before payment. $0.003 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Trade history and net USDC flow for an Arc token, last 24 h: buys, sells, distinct buyers and sellers per 1 h / 6 h / 24 h, the latest 30 trades, and each known Uniswap v4 pool's exact swap count with USDC in and out. $0.002 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Find a paid API for any task: one search over every x402 API on Coinbase Bazaar, Circle, Fuci Market, CRA and sellers listed on APEX Market, ranked by distinct wallets that paid in 30 days (one is often the seller's own test; 3+ is where customers start), with price, chains, calls per payer and whether it answered 402 when we called it. Up to 100 results. $0.002 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "arc_yield" (44 tools before, 45 now)
Yield on Arc before you deposit: every lending vault Circle Earn Kit lists on Arc (Morpho Vault V2) with its rate (Circle's figure), size, how much a depositor can actually withdraw at this block (read on chain), where its money is lent and a 24 h trail of what could be withdrawn. Refreshed every 15 minutes. $0.003 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Recently observed → Live
Changed the definition of "arc_fresh_launches"
⟨53 unchanged words⟩ $0.003 per call over x402 (USDC on Arc,onlyBase or Solana, or XNT on X1). Call once without `payment` for the terms ⟨10 unchanged words⟩
Live → Recently observed
Changed the definition of "arc_fresh_launches"
⟨53 unchanged words⟩ $0.003 per call over x402 (USDC on Arc,Base or Solana, or XNT on X1only). Call once without `payment` for the terms ⟨10 unchanged words⟩
Changed the definition of "arc_passport_confirm" and "arc_passport_draft"
Finish afreepassportArcyouAgentstartedPassport:beforeafter1yourOctwallet2026,sentafter the register() transaction fromarc_passport_draft,the old flow:
Added "arc_whale_feed" (43 tools before, 44 now)
Copy-trade signals on Arc: newest buys by the 25 most profitable wallets of the last 24 h, refreshed every 2 minutes, each with size, time, the wallet record and a simulated sell check where we have one. Reads only; you keep your keys. Not advice. $0.02 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "arc_seller_rank" and "arc_whales" (41 tools before, 43 now)
Which Arc agents are worth buying from: ranked by distinct OUTSIDE payers read from Arc settlements, with payments, USDC, payer concentration and whether the agent answers now. Track record, not price; concentrated and shared-payout cases are flagged. $0.005 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Arc wallets that made the most REALISED profit in the last 24 h (closed trades only, average cost), with win/loss, open cost and latest buys, refreshed hourly. Launch insiders (first buy within about a minute of the pool opening) and bot-like wallets are excluded; covers the USDC-paired pools we index. Not advice. $0.01 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "arc_trust_check" (40 tools before, 41 now)
Before paying an Arc agent: does it actually deliver? Measured, not claimed: answering now and over 7 days, response time, whether its Arc payment works, whether a real paid call by us settled, and who pays it on chain (outside payers, concentration, self-looking money). Pass agent, address or url. $0.003 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Changed the definition of "arc_ubi_payouts"
⟨37 unchanged words⟩ UBI, recent payouts (wallets, USDC).Pass an ArcAaddressper-wallettopayoutgetestimate (its UBIbalancereadliveonandArcitsjustestimatednow)share
Changed the definition of "arc_bundle_check" and "arc_fresh_launches"
⟨10 unchanged words⟩ of supply), wallets it funded that boughtinamong the first 60 swaps of the first two minutes (funding traced for the earliest 12 buyers), and the transactions. Pass token or pool. ⟨33 unchanged words⟩
⟨7 unchanged words⟩ a sell verdict from a real round trip and a bundle verdict (read from the first 60 swaps of the first two minutes and who funded the earliest 12 buyers; the evidence is in arc_bundle_check)
Added "arc_bundle_check" (39 tools before, 40 now)
Was this Arc launch bundled? The creator's own buy (share of supply), wallets it funded that bought in the first two minutes, and the transactions. Pass token or pool. $0.004 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Added "arc_ubi_payouts" (38 tools before, 39 now)
UBI (ubi.fun) holder payouts on Arc: USDC waiting in the payout contract, when the next payout list becomes valid and when it was fixed (UBI bought after that counts from the list after it), USDC per 1M UBI, recent payouts (wallets, USDC). Pass an Arc address to get its UBI balance read live and its estimated share of the next payout (pro rata over UBI outside the pool, burn address and ubi.fun hook; their list is computed off chain). Same numbers as apexfaucet.xyz/arc/ubi/. We hold UBI and say so.
Changed the definition of "erc8004_how_to"
How ERC-8004 works on Arc (and where the registry is on X1), from the spec and the deployed contracts: ⟨31 unchanged words⟩
Certificate recorded, valid to 2026-12-16
Authorization not required
Added "arc_agent_market", "arc_agent_reputation", "arc_agent_search" and 25 more; changed the definition of "arc_agent_status", "arc_exit_check_bulk", "arc_grow" and 1 more (10 tools before, 38 now)
⟨125 unchanged words⟩ for all agents in one call: /api/x402/arc-agent-watch ($1$0.004).
⟨21 unchanged words⟩ ). Returns x402 payment instructions for /api/x402/arc-exit-check-bulk ($1$0.025, USDC on Arc, USDC on Solana or ⟨8 unchanged words⟩
Verified owner set by well_known_file proof on apexfaucet.xyz
Unknown → Live
First tool surface recorded: 10 tools (server version 1.0.0)
https://apexfaucet.xyz/api/mcp/arc (mcp_streamable_http) — from mcp_registry, with the record
Showing the latest 33 events. The API returns up to 500 and filters by kind: ?kind=tool_surface_changed
⟨31 unchanged words⟩ Arc, USDC on Solana or XNT).Single checksForareonefreetokenviause arc_exit_check.
Give an agentRETIREDan1ERC-8004Octidentity2026:onan Arcfor free. Pass its name, what it does andAgentwherePassportitcostscan$0.99.beAreached;personwepayswritefrom acorrect registration file, host it, check that its endpoints answer, and return the unsigned register() transaction for Arc's identity registry. Thebrowser walletthat sendsatithttps://apexfaucet.xyz/arc/passport/owns;thean agentfrom the first block (about 0.004 USDC of gas; one claim from arc_faucet_claim coversbuys it).Then call arc_passport_confirmwiththe transactionarc_passport_buy.hash.ThisNotoolkeynoweveronlyleavesreturnsyourthatside.answer.
⟨2 unchanged words⟩ "description":"optional 0x address on Arc:itsreturnsUBIthebalanceexactandpaidestimatedcall for its payout estimate","type":"string"}},"type":"object"}
⟨73 unchanged words⟩ now; without it, the contract, ABI andsteps.steps, and priceCheck: APEX's price on Arc against its price on X1. While they are more than 10% apart, do not deposit (half the USDC would buy APEX at that premium); our own page refuses then.
Who actually pays whom on Arc. Everyx402-shapedsigned x402-style payment on Arc since launch, read from the ⟨4 unchanged words⟩ spent on Arc USDC and every Circle Gatewaybatch.batch (plain transfers carry no marker of what they paid for and are not counted). Without an address: the totals, each facilitator ⟨18 unchanged words⟩ where the same wallets pay and are paid;distributionconcentrated, one payertomakingmany;most of the volume; self; or contract flow), each measured and ⟨35 unchanged words⟩ with the latest 1,000 settlements: /api/x402/arc-x402 ($1$0.004).
The agent economy on Arc, mapped: every agent in the ERC-8004 registry that publishes a registration file, with its owner, services and whether it takes x402. $0.004 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
What other wallets have said about an Arc agent on chain: every ERC-8004 reputation entry for it (who gave it, the value, the tags, whether it was revoked) and the registry's own summary. Includes the weekly uptime records the APEX Watchtower writes. Free, 200 calls a day.
Find an agent on Arc by what it is called or where it answers: searches every agent in Arc's ERC-8004 registry that the APEX Watchtower checks each hour, and returns its id, status, uptime over measured hours, whether it can be paid on Arc and its main endpoint. Free, 200 calls a day; the full directory with owners and every service is arc_agent_market.
Who sells this on Arc, and for how much? Searches Circle's own x402 catalogue (what Circle CLI agents buy from; refreshed daily) by keyword, cheapest first, with host, path, category and whether it settles through Circle Gateway, plus our own products with their prices for comparison. Use it to price a service before you build or buy it. Free.
What bringing USDC into Arc over Circle CCTP really costs, measured from arrivals: every arrival with the amount credited and the fee taken, and observed fees by size. $0.004 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Before you approve, pay or trust a contract on Arc: is it really a contract, can someone change its code (EIP-1967 proxy implementation, admin and beacon slots), who is its owner(), and what token it says it is. Read live from the chain. Free, 200 calls a day.
Who is this Arc address as a trader? How often it is the first buyer into a new pool, how fast it enters, USDC in versus out, positions it is stuck in, and the flags. Facts from the chain, never a label. $0.004 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Who launched what on Arc and whether any of it ever traded: every repeat creator with their launches and the swap fees those launches earned. $0.004 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Who settles x402 payments on Arc, measured on the chain: every relayer that spent an EIP-3009 authorization on Arc USDC, with its label where one is published, how many settlements, payers and payees, volume, and the shape of its flow (direct, circular, concentrated, self or contract). Plus Circle's two facilitators and what each needs. Free.
Arc launchpad fee vaults: every vault holding USDC now, its creator and token, and how much it changed since our previous scan. Fees only accrue from real swaps. $0.025 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Arc launches in real time, each with a sell verdict from a real round trip, so you see the new pools that can actually be exited. $0.003 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
What a transaction on Arc actually costs, measured from real receipts rather than quoted from the docs: percentiles per transaction kind, with the sample sizes. $0.004 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
The Arc pool graveyard: every pool we measured with its state (empty or alive) and lifetime volume, so you know which ones nothing can be sold into. $0.025 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
What a Uniswap v4 hook on Arc is allowed to do, read from the permission bits in its address with no chain call: whether it runs on swaps or can rewrite amounts. A capability, not a verdict. $0.003 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Every token symbol on Arc worn by more than one contract, with how many contracts share it and the canonical address where one is verified. Identity is the contract, never the symbol. $0.004 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
An agent buys its own ERC-8004 identity on Arc with a signature alone: $0.99 over x402, paid in USDC on Arc or Base. We host a correct registration file, mint the identity and hand it to the wallet that signed the payment, never to a typed address, and answer with the agentId and both transactions. Call once without `payment` to get the x402 terms, sign them, call again with `payment`. A refused input is never charged.
Finish a free Arc Agent Passport: after your wallet sent the register() transaction from arc_passport_draft, pass the draft slug and the transaction hash. We read the receipt on Arc (never the caller's word), fill the file with the new agentId and return the passport page, its share picture, the watchtower check-up and its tower in Arc City. Free.
Give an agent an ERC-8004 identity on Arc for free. Pass its name, what it does and where it can be reached; we write a correct registration file, host it, check that its endpoints answer, and return the unsigned register() transaction for Arc's identity registry. The wallet that sends it owns the agent from the first block (about 0.004 USDC of gas; one claim from arc_faucet_claim covers it). Then call arc_passport_confirm with the transaction hash. No key ever leaves your side.
Look up an Arc Agent Passport by agentId or draft slug: its registration file, owner, endpoints, whether it is active, and its links (passport page, share picture, hourly check-up, tower in Arc City). Free.
Did that Arc payment really land? Payer, recipient, amount in both of Arc's transfer forms (the ERC-20 view and the native log), confirmation and gas, checked against what you expected. $0.003 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Which Arc RPC is answering right now, and how fast: the latest block, how far each one lags and its response time, measured this minute from our server. Arc's official RPC throttles in a way that reads like a bug ("Request exceeds defined limit"); use this to pick another. Free.
How many stablecoins exist on Arc right now, read from the contracts: USDC and EURC total supply, their addresses and the EIP-712 signing domains a payment signs against. Free.
Should you buy this Arc pool? One call, one 0-100 answer from the hook's permissions, a real sell probe and what happened to earlier buyers, with every input shown. $0.004 per call over x402 (USDC on Arc, Base or Solana, or XNT on X1). Call once without `payment` for the terms, sign them with your own wallet, call again with `payment`.
Everything public about one Arc address in one call: USDC (native, 18 decimals) and EURC and APEX balances, whether it is a contract, how many ERC-8004 agent identities it owns and which agents, and whether it sells over x402 on Arc. Read live from the chain. Free, 200 calls a day.
How ERC-8004 works on Arc, from the spec and the deployed contracts: register an agent (and the one-call shortcuts), the registration file fields, proving your endpoint domain, pointing payments at an agentWallet, writing and reading reputation, and what explorers like 8004scan read. Free.
How to get USDC onto Arc, every route we know works: a free claim at our faucet (a signature, no gas), bridges measured live, Circle CCTP and what it really costs at small size, Circle Gateway balances, and Circle's Onramp Kit for apps that let people pay by card or Apple Pay. Free.
How to accept x402 payments on Arc, from what we verified on chain while doing it ourselves: the USDC and EURC signing domains, what a settlement leaves in the logs, what one costs in gas, and your three ways to settle (yourself, Circle Facilitator Service, Circle Gateway nanopayments). Free.
How do I pay this URL? Point it at any x402 paywall and get its terms read for you: protocol version, every network and asset it accepts with the real amount, the address it pays, and how to pay each option (EIP-3009 signature, Circle Gateway batch, Solana fee payer). It also lists what is wrong with the paywall, e.g. a missing signing domain. Free, 100 calls a day.