io.github.send21ioPublished by GitHub account send21iov1.7.0Updated Nov 8, 2026
Crypto pay links and API for people and AI agents. BTC, Lightning, USDC, USDT, EURC, SOL, ETH.
Remote send21 server that lets an assistant prepare crypto pay links and non-custodial payment drafts for BTC, Lightning, USDC, USDT, EURC, SOL and ETH.
Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.
Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.
Read https://sourceweft.com/mcp/io.github.send21io%2Fmcp/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.Add this to your client's mcpServers config.
{
"mcpServers": {
"send21": {
"type": "http",
"url": "https://send21.io/mcp"
}
}
}[send21 MCP server] [Listed on mcpservers.org]
Remote Model Context Protocol server for send21: crypto pay links and API for people and AI agents.
send21 prepares payment instructions for BTC (on-chain and Lightning), USDC, USDT, EURC, SOL and ETH. The payer signs in their own wallet. send21 never holds keys, never signs, and never broadcasts.
Live endpoint (Streamable HTTP): https://send21.io/mcp (API key), https://send21.io/mcp/oauth (OAuth sign-in)
Descriptor: https://send21.io/.well-known/mcp.json
Agent docs: https://send21.io/llms.txt
OpenAPI: https://send21.io/swagger/v1/swagger.json
Site: https://send21.io
Point an MCP client at the remote server:
Auth: API key or OAuth sign-in.
s21_…) and send them as above.https://send21.io/mcp/oauth with no headers; see Sign in instead of an API key below.drafts:write, drafts:read, webhooks:manage cannot move funds.tools/list and get_fee_schedule work without authentication.Clients that support MCP sign-in (OAuth) can connect to https://send21.io/mcp/oauth with no key and no headers. The client opens send21 in your browser; you sign in, see what the app asks for, and approve. A connected app only ever uses receiving addresses you approved. It is listed under API keys as a connected app, where Disconnect ends it at once, and a connection nobody uses for 90 days ends by itself.
Claude Code
Cursor (.cursor/mcp.json in your project, or ~/.cursor/mcp.json for all projects)
VS Code (.vscode/mcp.json)
Any MCP client that supports OAuth: add https://send21.io/mcp/oauth as a remote (Streamable HTTP) MCP server with no headers, then sign in when the client asks.
Prefer an API key? It still works: use https://send21.io/mcp with Authorization: Bearer s21_..., a scoped key you create at https://send21.io/api-keys in your account. tools/list and get_fee_schedule work without either. Details: https://send21.io/docs/mcp
14 tools (see live tools/list): create_draft, get_draft, get_draft_status, list_draft_quotes, get_transaction_template, submit_lightning_proof, create_payment_request, get_payment_request, list_address_book, propose_receiving_address, get_account_status, create_account, get_rate, get_fee_schedule. Signing and broadcast stay in the user’s wallet.
Agents onboard themselves; humans approve where the money lands. An agent proposes a receiving address (propose_receiving_address) and the owner approves it after signing in, with a passkey or an authenticator code; no API key can approve an address, and any other address is refused (422 address_not_approved). An agent without a key can sign its owner up (create_account), but it cannot create anything until the owner takes the account over from an emailed link (403 owner_not_confirmed until then). Details: https://send21.io/docs/mcp
send21: crypto pay links and API for people and AI agents.
Contact: [email protected]
MIT
Source: README.md at commit d03869e
Get wallet payment instructions
Get the transaction template for an on-chain draft: every output to pay, plus walletcreatefundedpsbt arguments and a pay-to-many CSV on Bitcoin, or payment URIs (and calldata on EVM chains) on Solana, Ethereum, Base, Arbitrum and Polygon. The sender's own wallet funds, reviews and signs it; send21 contains no signing code. Not for Lightning drafts (pay their invoice). Requires scope drafts:read.
draftIdrequiredGet fee schedule
Get the public send21 fee schedule: tiered percent by payment size in USD, min/max fee, and dust limit. No authentication needed.
Takes no parameters.
Create pay link
Create a payment request / checkout pay link (you are the RECEIVER asking to get paid). Price in any of 161 fiat currencies; the payer opens the returned payPath, picks one of the offered currencies (rate locks then), and pays a single QR-scannable transfer straight to your address. On accounts with the policy ApprovedOnly (see get_account_status) every address must be one of the owner's approved receiving addresses; otherwise the answer is 422 address_not_approved and nothing is created (propose it with propose_receiving_address). Requires scope drafts:write.
memooptionsrequiredorderIdfiatAmountrequireddeclineNoteexpiryHoursfiatCurrencyrequiredidempotencyKeyreuseOpenForOrdershortfallAbsorbUpToPercentPropose receiving address
Propose an address for the owner to approve: one of the owner's own receiving addresses (for pay links) or the address of someone the owner pays (for drafts). It is saved unapproved and the owner gets an email. On accounts with the policy ApprovedOnly, API keys can only use approved addresses, and only the owner can approve one, signed in to the send21 app with a passkey or authenticator code. No key can approve an address. Requires scope addressbook:write.
labelrequiredaddressrequirednetworkrequireddirectionGet account status
What stands between you and a live pay link: whether the owner's email is confirmed, the receiving-address policy, how many addresses are approved or waiting for approval, unsettled fees, your key's scopes, and the next steps. Requires scope drafts:read.
Takes no parameters.
List address book
List the account's saved addresses (label, address, network, direction: Sending = recipients the owner pays, Receiving = the owner's own addresses). Requires scope addressbook:read.
Takes no parameters.
Get payment draft
Get a payment draft by id, including amounts, fee, quote, and status. Requires scope drafts:read.
draftIdrequiredSubmit Lightning payment proof
Confirm a paid Lightning draft with its proof of payment: the 64-character preimage the paying wallet shows after a Lightning payment. Needed for drafts with a pasted bolt11 invoice, and for Lightning addresses whose provider does not report payments. send21 checks that SHA-256 of the preimage equals the invoice's payment hash; the draft then confirms within about 30 seconds. Requires scope drafts:write.
draftIdrequiredpreimagerequiredCreate send21 account for owner
Create a send21 account for your human owner, without a key. The owner gets an email with a link to take the account over; until they do, nothing can be created. Returns a bootstrap API key ONCE (save it and send it as Authorization: Bearer on every later call; reconnect this MCP client with it). The key can read, propose addresses and check get_account_status; it can create pay links only after the owner took the account over and approved a receiving address you proposed. Agents onboard themselves; humans approve where the money lands. If the email already has an account, ask the owner for an API key instead.
agentNameownerEmailrequiredintendedUseGet pay link
Get a payment request by id: status (Open/Completed/Cancelled/Expired), pay path, offered currencies, and the underlying draft once the payer committed. Includes changeSignals and changeNotes: what is unusual compared with the account's paid payments (new_address, new_asset, unusual_amount), the same lines the payer sees on the pay page; empty when nothing is unusual. Requires scope drafts:read.
paymentRequestIdrequiredGet exchange rate
Get the current exchange rate for an asset in a fiat currency (rate = fiat units per 1 whole asset unit, with source provenance). Assets: Btc, Usdc, Usdt, Eurc, Sol, Eth. 161 ISO 4217 fiat currencies are supported. Requires an API key.
assetrequiredfiatCurrencyrequiredCreate payment draft
Create a non-custodial payment draft (you are the SENDER paying a receiver address). Amount is either exact base units (sats for BTC, micro-units for stablecoins, lamports for SOL, gwei for ETH) via amountBaseUnits, or fiat-pegged via fiatCurrency+fiatAmount with the exchange rate locked at creation. Returns the draft incl. id, amounts, fee, and status. Funds move only when the sender signs in their own wallet. send21 never holds keys. On accounts with the policy ApprovedOnly the receiver must be an address the owner approved (422 address_not_approved otherwise). Requires scope drafts:write.
memonetworkrequiredcurrencyfiatAmountfiatCurrencyidempotencyKeyamountBaseUnitsreceiverAddressrequiredshortfallAbsorbUpToPercentList draft quotes
List every quote (rate lock) of a fiat-priced draft, oldest first. Quotes never change; a re-quote adds a new one with its own id. Each has a sha256 (RFC 8785 JCS + SHA-256). Requires scope drafts:read.
draftIdrequiredGet draft status
Lightweight status snapshot of a draft: status (AwaitingPayment/Seen/Confirmed/Expired/Cancelled), paying txid, confirmations, and reviewState when a transfer with a different amount arrived (pending = needs the receiver's decision and the draft is not paid; accepted; rejected; unresolved = the draft expired while undecided, the money is with the receiver). Cheap to poll. Requires scope drafts:read.
draftIdrequired100% of the applicable checks met
How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.
A hosted service is used under its provider's terms, so no license is expected here. This check is left out of the percentage.
{ "mcpServers": { "send21": { "url": "https://send21.io/mcp", "transport": "streamable-http", "headers": { "Authorization": "Bearer s21_YOUR_API_KEY" } } }}claude mcp add --transport http send21 https://send21.io/mcp/oauth# then run /mcp in Claude Code and choose send21 to sign in# (or, from your shell: claude mcp login send21){ "mcpServers": { "send21": { "url": "https://send21.io/mcp/oauth" } }}{ "servers": { "send21": { "type": "http", "url": "https://send21.io/mcp/oauth" } }}