send21
Description
Non-custodial payment drafts/pay links for BTC, USDC, USDT, EURC. Never holds keys.
What our measurements say
send21 is a remote MCP server published at send21.io. It has been probed 6 times since 9/12/2026. It answered in 6 of them (100.0%), a near-uninterrupted record. Median response time is 213 ms, placing it among the faster endpoints. It offers a narrow, focused set of 9 tools. On the protocol side it speaks the 2026-07-28 stateless spec.
Agent readability score
Can an LLM agent pick the right tool here — names, descriptions and parameter clarity are assessed.
Agent readability score
Agent readability score
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| Run | Era | Modern | ms | Legacy | ms | Versions |
|---|---|---|---|---|---|---|
| 2026-09-13 01:33:33 | Dual-era | 200 | 161 | 200 | 161 | 2026-07-28 |
| 2026-09-12 23:31:36 | Dual-era | 200 | 167 | 200 | 160 | 2026-07-28 |
| 2026-09-12 21:29:15 | Dual-era | 200 | 213 | 200 | 225 | 2026-07-28 |
| 2026-09-12 19:27:29 | Dual-era | 200 | 405 | 200 | 402 | 2026-07-28 |
| 2026-09-12 17:24:09 | Dual-era | 200 | 245 | 200 | 259 | 2026-07-28 |
| 2026-09-12 15:21:42 | Dual-era | 200 | 202 | 200 | 170 | 2026-07-28 |
Schema compliance
tools/list structure, inputSchema validity, and a functional smoke test — the components of the 0-100 score.
- tools/list schema valid
- inputSchema is valid JSON Schema
- Smoke test not run this round
- Cold-start: cold 45ms → warm 57ms (penalty 0ms)
Tools
Tools the server advertised in the latest measurement — measured, not catalog-claimed.
get_transaction_templateGet the multi-output transaction template for a draft: Bitcoin Core walletcreatefundedpsbt arguments and Electrum/Sparrow pay-to-many CSV. The operator's wallet funds, reviews, and signs it — send21 contains no signing code. Requires scope drafts:read.
draftIdstringrequired
get_fee_scheduleGet the public send21 fee schedule: tiered percent by payment size in USD, min/max fee, and dust limit. No authentication needed.
create_payment_requestCreate a payment request / checkout pay link (you are the RECEIVER asking to get paid). Price in any of 165 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. Requires scope drafts:write.
fiatCurrencystringrequiredfiatAmountnumberrequiredoptionsarrayrequiredorderIdstringrequiredmemostringrequiredexpiryHoursintegerrequiredidempotencyKeystringrequired
list_address_bookList the account's saved addresses (label, address, network, direction: Sending = recipients the owner pays, Receiving = the owner's own addresses). Requires scope addressbook:read.
get_draftGet a payment draft by id, including amounts, fee, quote, and status. Requires scope drafts:read.
draftIdstringrequired
get_payment_requestGet a payment request by id: status (Open/Completed/Cancelled/Expired), pay path, offered currencies, and the underlying draft once the payer committed. Requires scope drafts:read.
paymentRequestIdstringrequired
get_rateGet 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. 165 ISO-4217 fiat currencies are supported.
fiatCurrencystringrequiredassetstringrequired
create_draftCreate 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) 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. Requires scope drafts:write.
receiverAddressstringrequirednetworkstringrequiredcurrencystringrequiredamountBaseUnitsintegerrequiredfiatCurrencystringrequiredfiatAmountnumberrequiredmemostringrequiredidempotencyKeystringrequired
get_draft_statusLightweight status snapshot of a draft: status (AwaitingPayment/Seen/Confirmed/Expired/Cancelled), paying txid, confirmations. Cheap to poll. Requires scope drafts:read.
draftIdstringrequired
Availability history
Each block is one measurement round. Green: working response. Amber: responded but the server was returning errors (5xx). Red: no response at all.
Era history
Each cell is one probe run. Faded cells are incomplete probes — one leg did not answer, so the era is inconclusive.
Response time history
The two probe legs separately: modern server/discover and legacy initialize.
Event log
Derived by comparing consecutive probes — changes in era, protocol version, build and reachability.
- Added to watch — era: Dual-era
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[](https://mcpmetrics.io/servers/io-github-send21io-mcp)<a href="https://mcpmetrics.io/servers/io-github-send21io-mcp"><img src="https://mcpmetrics.io/badge/io.github.send21io/mcp/era.svg" alt="mcpmetrics"></a>You are seeing the last 7 days. Sign up for the full history. Which check failed and why is in the dashboard.
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