send21
REMOTE · SEND21.IO · SCANNED SEP 20
Non-custodial payment drafts/pay links for BTC, USDC, USDT, EURC. Never holds keys.
Available components
How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. How we score → Why this is hard to score →
Endpoint Security63
- The endpoint's TLS certificate is valid, in date, and uses a strong key. View diagnostics → Pass
- Authorisation not fully verified: no authorisation is required to call this server, and 9 tool(s) never declared a destructiveHint. The MCP spec treats an absent hint as destructive by default, so we cannot call this surface safe. See how to fix → View diagnostics → Unverified
- HTTPS is enforced; there's no plaintext access path. View diagnostics → Pass
- The HSTS (Strict-Transport-Security) header is present. View diagnostics → Pass
- DNSSEC check failed: this domain isn't protected by DNSSEC. See how to fix → View diagnostics → Fail
Transport & Reachability100
- Verified streamable-http transport via a live MCP handshake. View diagnostics → Pass
Schema Quality & AI Usability80
- AI-judged instruction clarity (excellent).Pass
- Tool/resource definitions use about 957 tokens (~106/item across 9 items; 9 tools + 0 resources), lean.Pass
- Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management47
- Stability observed for 14 of 30 days with no destabilising changes; credit accrues until the full window elapses.Partial
Tool Coverage100
- 100% of tools have a non-trivial description (not blank, and not just the tool's name).Pass
- 100% of tool parameters carry a description.Pass
Tool Safety100
- No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.Pass
- We read all 9 captured tool definition(s), and no name or description among them implies an irreversible operation.Pass
- An AI judge read all 9 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities100
- Implements a current MCP spec version (2026-07-28).Pass
How do I install the send21 MCP server?
send21 is a hosted endpoint at https://send21.io/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.
remote · send21.io
claude mcp add --transport http send21io-mcp 'https://send21.io/mcp'
{
"mcpServers": {
"send21io-mcp": {
"url": "https://send21.io/mcp"
}
}
} {
"servers": {
"send21io-mcp": {
"type": "http",
"url": "https://send21.io/mcp"
}
}
} [mcp_servers.send21io-mcp] url = "https://send21.io/mcp"
{
"$schema": "https://opencode.ai/config.json",
"mcp": {
"send21io-mcp": {
"type": "remote",
"url": "https://send21.io/mcp",
"enabled": true
}
}
} openclaw mcp add send21io-mcp --url 'https://send21.io/mcp' --transport streamable-http
mcp_servers:
send21io-mcp:
url: "https://send21.io/mcp" {
"McpServers": {
"send21io-mcp": {
"Transport": "http",
"Url": "https://send21.io/mcp"
}
}
} assistant mcp add send21io-mcp -t streamable-http -u 'https://send21.io/mcp'
{
"mcpServers": {
"send21io-mcp": {
"type": "http",
"url": "https://send21.io/mcp"
}
}
} The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.
Every change we have recorded for this component, newest first. Security-relevant changes are always shown. ▲ marks a change for the better, ▼ a change for the worse; unmarked changes are neutral.
- 19 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 40 to 43. That category is still filling its 30-day observation window: 12 days of observed history at the previous scan, 13 at this one. The score rises as the window fills, whether or not the server changes.
- 17 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 33 to 37. That category is still filling its 30-day observation window: 10 days of observed history at the previous scan, 11 at this one. The score rises as the window fills, whether or not the server changes.
- 15 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 27 to 30. That category is still filling its 30-day observation window: 8 days of observed history at the previous scan, 9 at this one. The score rises as the window fills, whether or not the server changes.
- 13 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 20 to 23. That category is still filling its 30-day observation window: 6 days of observed history at the previous scan, 7 at this one. The score rises as the window fills, whether or not the server changes.
- 11 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 13 to 17. That category is still filling its 30-day observation window: 4 days of observed history at the previous scan, 5 at this one. The score rises as the window fills, whether or not the server changes.
- 8 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 3 to 7. That category is still filling its 30-day observation window: 1 days of observed history at the previous scan, 2 at this one. The score rises as the window fills, whether or not the server changes.
- 7 Sept 26 0
- Stability: unverified → 0.03 ▲ functional
- 6 Sept 26 68
First indexed and scored.
Diagnostic detail from the automated scan of this channel: what the scanner observed at each step, so you can see exactly where a check passed or failed. It is informational only and never changes the trust score.
Captured 20 Sept 2026 · Probed https://send21.io/mcp
TLS valid
Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .
| Subject | Issuer | Valid from | Valid until | Key | Signature | Serial |
|---|---|---|---|---|---|---|
| CN=send21.io | CN=WE1,O=Google Trust Services,C=US | 9 Aug 2026 | 7 Nov 2026 | ECDSA 256 | ECDSA-SHA256 | 6fc69e7a3dc0c3ca13ce4e22028ad967 |
| SANs: send21.io, *.send21.io | ||||||
| CN=WE1,O=Google Trust Services,C=US (CA) | CN=GTS Root R4,O=Google Trust Services LLC,C=US | 13 Dec 2023 | 20 Feb 2029 | ECDSA 256 | ECDSA-SHA384 | 7ff31977972c224a76155d13b6d685e3 |
| CN=GTS Root R4,O=Google Trust Services LLC,C=US (CA) | CN=GlobalSign Root CA,OU=Root CA,O=GlobalSign nv-sa,C=BE | 15 Nov 2023 | 28 Jan 2028 | ECDSA 384 | SHA256-RSA | 7fe530bf331343bedd821610493d8a1b |
Background: What to check on a remote MCP endpoint →
DNSSEC insecure
Validation of send21.io. — Not signed
| Zone | DS | Keys | Algorithms | Outcome |
|---|---|---|---|---|
| . | trust_anchor | 20326, 38696 | 8, 8 | Verified |
| io. | present | 57355 | 8 | Verified |
| send21.io. | absent | Unsigned (proven) parent-signed NSEC/NSEC3 proves an unsigned delegation |
Authentication No authorisation required
The endpoint answered without asking for a token. Anyone who knows the URL can reach it.
| Result | No authorisation required |
|---|---|
| HTTP status | 200 |
| Header | Value |
|---|---|
| strict-transport-security | max-age=63072000; includeSubDomains |
| content-security-policy | default-src 'none'; frame-ancestors 'none' |
| x-content-type-options | nosniff |
| x-frame-options | DENY |
| referrer-policy | no-referrer |
| permissions-policy | camera=(), microphone=(), geolocation=() |
Background: How OAuth 2.1 works in the 2026 MCP spec →
Transports 2 probes
| Transport | URL | Outcome | Status | Location |
|---|---|---|---|---|
| streamable-http | https://send21.io/mcp | Verified | 200 | |
| http (plaintext) | http://send21.io/mcp | HTTPS enforced |
The tools this component advertises to a client, with an estimated token cost for each. Expand a tool to see its parameters and schema. The per-tool counts are indicative and are not scored directly; the schema's total context footprint is one signal in Schema Quality & AI Usability. A tool's description is untrusted text the model reads on every call, which is what makes this list a security surface and not just an inventory: how tool poisoning works →
create_draft ~317
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) 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.
| Name | Type | Req | Description |
|---|---|---|---|
| amountBaseUnits | integer|null | yes | Exact amount in base units (sats / micro-units); omit when using fiat pricing |
| currency | string|null | yes | Asset: Btc (default), Usdc, Usdt, or Eurc |
| fiatAmount | number|null | yes | Fiat amount; requires fiatCurrency |
| fiatCurrency | string|null | yes | Fiat currency code for fiat-pegged amount, e.g. USD |
| idempotencyKey | string|null | yes | Idempotency key — retries with the same key return the original draft |
| memo | string|null | yes | Free-text memo shown on the draft (max 500 chars) |
| network | string | yes | Network: Mainnet, Solana, Ethereum, Base (test: Testnet4, Signet, Regtest, SolanaDevnet, EthereumSepolia, BaseSepolia) |
| receiverAddress | string | yes | Receiver address (Bitcoin bc1…, Solana base58, or 0x… for Ethereum/Base) |
No output schema declared.
No examples provided.
create_payment_request ~215
Create 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.
| Name | Type | Req | Description |
|---|---|---|---|
| expiryHours | integer|null | yes | Hours until the request expires (default 24) |
| fiatAmount | number | yes | Amount in the fiat currency |
| fiatCurrency | string | yes | Fiat currency the request is priced in, e.g. USD, EUR, SEK |
| idempotencyKey | string|null | yes | Idempotency key — retries with the same key return the original request |
| memo | string|null | yes | Message shown to the payer (max 500 chars) |
| options | array | yes | Currencies the payer may choose from, each with your receiving address |
| orderId | string|null | yes | Your own order/reference id — echoed in webhooks for reconciliation |
No output schema declared.
No examples provided.
get_draft ~44
Get a payment draft by id, including amounts, fee, quote, and status. Requires scope drafts:read.
| Name | Type | Req | Description |
|---|---|---|---|
| draftId | string | yes | Draft id (GUID) |
No output schema declared.
No examples provided.
get_draft_status ~59
Lightweight status snapshot of a draft: status (AwaitingPayment/Seen/Confirmed/Expired/Cancelled), paying txid, confirmations. Cheap to poll. Requires scope drafts:read.
| Name | Type | Req | Description |
|---|---|---|---|
| draftId | string | yes | Draft id (GUID) |
No output schema declared.
No examples provided.
get_fee_schedule ~38
Get the public send21 fee schedule: tiered percent by payment size in USD, min/max fee, and dust limit. No authentication needed.
Input schema present but exposes no named parameters.
No output schema declared.
No examples provided.
get_payment_request ~61
Get 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.
| Name | Type | Req | Description |
|---|---|---|---|
| paymentRequestId | string | yes | Payment request id (GUID) |
No output schema declared.
No examples provided.
get_rate ~102
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. 165 ISO-4217 fiat currencies are supported.
| Name | Type | Req | Description |
|---|---|---|---|
| asset | string | yes | Asset: Btc, Usdc, Usdt, or Eurc |
| fiatCurrency | string | yes | Fiat currency code, e.g. USD, EUR, SEK |
No output schema declared.
No examples provided.
get_transaction_template ~76
Get 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.
| Name | Type | Req | Description |
|---|---|---|---|
| draftId | string | yes | Draft id (GUID) |
No output schema declared.
No examples provided.
list_address_book ~45
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.
Input schema present but exposes no named parameters.
No output schema declared.
No examples provided.
What is the send21 MCP server?
send21 is an MCP server listed in the public MCP registry as io.github.send21io/mcp. Non-custodial payment drafts/pay links for BTC, USDC, USDT, EURC. Never holds keys. This page covers its hosted endpoint (https://send21.io/mcp).
Is the send21 MCP server safe to use?
send21 scores 74 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.
What tools does the send21 MCP server expose?
send21 exposes 9 tools: get_transaction_template, get_fee_schedule, create_payment_request, list_address_book, get_draft, and 4 more. Their descriptions and schemas cost roughly 957 tokens of context every time the server is loaded.
Does the send21 MCP server require authentication?
No. We connected to send21 without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.
Is the send21 MCP server still maintained?
send21 is still listed as active in the MCP registry. We last reached this channel on 20 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.