send21 is answering right now. Last checked 10 min ago. It exposes 14 tools. Last commit 13 Oct 2026.
Crypto pay links and API for people and AI agents. BTC, Lightning, USDC, USDT, EURC, SOL, ETH.
Uptime history
57 days of history · worst day 93%
57 days agonow
100.0%
Uptime 24h
182 of 182 checks
14
Tools
read from the server
152 ms
Response time
average over 24h
0
Stars
last commit 13 Oct 2026
What changed 34
Every tool that appeared, vanished or quietly changed what it asks for. Recorded since 2 October 2026. No other catalogue keeps this.
22 Oct
a tool changed version2 times that day
20 Oct
3 tools appeared
create_account, get_account_status, propose_receiving_address
20 Oct
2 tool descriptions were rewritten
create_draft, create_payment_request
20 Oct
a tool changed version2 times that day
19 Oct
a tool changed version
13 Oct
2 tools changed the parameters they ask for4 times that day
create_draft, create_payment_request
12 Oct
2 tools changed the parameters they ask for3 times that day
create_draft, create_payment_request
12 Oct
2 tool descriptions were rewritten
get_draft_status, get_payment_request
12 Oct
a tool appeared
list_draft_quotes
7 Oct
3 tool descriptions were rewritten
create_payment_request, get_rate, get_transaction_template
and 16 more, back to 2 October 2026
send21 missed one check this week
Everything else answered, so this is steady rather than shaky. We check every 15 minutes, which is how a one-off gets told apart from the start of a pattern, and how you hear about the next one within the hour instead of from your users.
Connect this server
Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 10 min ago.
run in your terminal
claude mcp add mcp --transport http https://send21.io/mcpSettings → Connectors → Add custom connector, then paste this address
https://send21.io/mcp~/.codex/config.toml
[mcp_servers.mcp]
url = "https://send21.io/mcp".cursor/mcp.json
{
"mcpServers": {
"mcp": {
"url": "https://send21.io/mcp"
}
}
}.vscode/mcp.json
{
"servers": {
"mcp": {
"type": "http",
"url": "https://send21.io/mcp"
}
}
}This endpoint answered with an authorization challenge. The server is running, and it signs you in through your browser: there is no API key to paste.
This server publishes 1 more address. The block above uses the one we reach during checks; the full list is under Endpoints below, and the author may intend a particular one for your client.
Available tools 14
Read directly from the server with tools/list, grouped by what they act on.
If a tool disappears, we record the date.
draft
create_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.
get_draft
Get a payment draft by id, including amounts, fee, quote, and status. Requires scope drafts:read.
get_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.
list_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.
account
create_account
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.
get_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.
payment
create_payment_request
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.
get_payment_request
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.
address
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.
fee
get_fee_schedule
Get the public send21 fee schedule: tiered percent by payment size in USD, min/max fee, and dust limit. No authentication needed.
propose
propose_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.
rate
get_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.
submit
submit_lightning_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.
transaction
get_transaction_template
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.
Endpoints
| URL | Transport | State | Latency | Checked |
|---|---|---|---|---|
| https://send21.io/mcp | streamable-http | answering | 111 ms | 10 min ago |
| https://send21.io/mcp/oauth | streamable-http | sign-in | 107 ms | 11 min ago |
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send21 — questions
Answers built from our own checks of this server.
What can send21 do?
It exposes 14 tools, read directly from the server on our last check. Among them: create_account, create_draft, create_payment_request, get_account_status, get_draft, get_draft_status and 8 more. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README.
How MCP servers expose tools in the first place →
What is send21 mostly used for?
Its tools cluster around draft, account and payment. That is what this server is built to work with — the grouping comes from the actual tool names, not from a category we assigned.
Is send21 working right now?
We send a real MCP handshake every 15 minutes. Over the last 24 hours 182 of 182 checks got a reply (100.0%), average response time 152 ms. The bar chart above shows every period we have measured.
How do I connect send21?
Copy the ready config from this page. We generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each in the form that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address. You sign in through your browser once and the client keeps the session: no key to copy, and it refuses anonymous clients.
How do you sign in to send21?
No API key is involved. send21 answers our knock with an OAuth challenge, so you authorise it once in your browser and the client keeps the session. That is also why we see no tool list: it will not describe itself to an anonymous client, and that is the server working as intended, not a fault.
How fast is send21?
It answers our handshake in 152 ms on average, which is faster than 82% of all working MCP servers we measure. That puts it in the quick quarter of the ecosystem. The comparison comes from our own checks across the whole registry, every 15 minutes.
Is send21 open source?
The code is open source: it is published under the MIT licence and 0 stars on GitHub. The licence covers the code in the repository, not the hosted service at send21.io, which runs on its operator's own terms.