io.usefulapi/numeral
REMOTE · NUMERAL.USEFULAPI.IO · SCANNED SEP 20
Calculate sales tax & VAT, record transactions and refunds, manage products and customers.
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 Security78
- The endpoint's TLS certificate is valid, in date, and uses a strong key. View diagnostics → Pass
- Authorisation is enforced on tool calls, advertised via RFC 9728 protected-resource metadata. Discovery is public, which costs nothing: no tool can be invoked without a token. View diagnostics → Pass
- HTTPS enforcement could not be verified: the plaintext port answered with HTTP 401, which proves neither a plaintext path nor enforcement. View diagnostics → Unverified
- HSTS check failed: the Strict-Transport-Security header is absent. See how to fix → View diagnostics → Fail
- DNSSEC check failed: this domain isn't protected by DNSSEC. See how to fix → View diagnostics → Fail
- The authorisation server offers only Dynamic Client Registration (RFC 7591), which MCP 2026-07-28 deprecated in favour of Client ID Metadata Documents. View diagnostics → Partial
Transport & Reachability100
- Verified streamable-http transport via a live MCP handshake. View diagnostics → Pass
Schema Quality & AI Usability81
- AI-judged instruction clarity (excellent).Pass
- Tool/resource definitions use about 1113 tokens (~101/item across 11 items; 11 tools + 0 resources), lean.Pass
- Usage-examples check failed: none of the tools include examples. See how to fix → Fail
Stability & Change Management63
- Stability observed for 19 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
- All 1 tool(s) whose name or description implies an irreversible operation declare an MCP destructiveHint annotation.Pass
- An AI judge read all 11 captured unit(s) of tool text and found none that tries to manipulate the model reading it.Pass
Capabilities60
- Spec-recency check failed: implements MCP spec 2025-06-18; the latest is 2026-07-28. See how to fix → Fail
How do I install the io.usefulapi/numeral MCP server?
io.usefulapi/numeral is a hosted endpoint at https://numeral.usefulapi.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 · numeral.usefulapi.io
claude mcp add --transport http io-usefulapi-numeral 'https://numeral.usefulapi.io/mcp'
{
"mcpServers": {
"io-usefulapi-numeral": {
"url": "https://numeral.usefulapi.io/mcp"
}
}
} {
"servers": {
"io-usefulapi-numeral": {
"type": "http",
"url": "https://numeral.usefulapi.io/mcp"
}
}
} [mcp_servers.io-usefulapi-numeral] url = "https://numeral.usefulapi.io/mcp"
{
"$schema": "https://opencode.ai/config.json",
"mcp": {
"io-usefulapi-numeral": {
"type": "remote",
"url": "https://numeral.usefulapi.io/mcp",
"enabled": true
}
}
} openclaw mcp add io-usefulapi-numeral --url 'https://numeral.usefulapi.io/mcp' --transport streamable-http
mcp_servers:
io-usefulapi-numeral:
url: "https://numeral.usefulapi.io/mcp" {
"McpServers": {
"io-usefulapi-numeral": {
"Transport": "http",
"Url": "https://numeral.usefulapi.io/mcp"
}
}
} assistant mcp add io-usefulapi-numeral -t streamable-http -u 'https://numeral.usefulapi.io/mcp'
{
"mcpServers": {
"io-usefulapi-numeral": {
"type": "http",
"url": "https://numeral.usefulapi.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 57 to 60. That category is still filling its 30-day observation window: 17 days of observed history at the previous scan, 18 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 50 to 53. That category is still filling its 30-day observation window: 15 days of observed history at the previous scan, 16 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 43 to 47. That category is still filling its 30-day observation window: 13 days of observed history at the previous scan, 14 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 37 to 40. That category is still filling its 30-day observation window: 11 days of observed history at the previous scan, 12 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 30 to 33. That category is still filling its 30-day observation window: 9 days of observed history at the previous scan, 10 at this one. The score rises as the window fills, whether or not the server changes.
- 9 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 23 to 27. That category is still filling its 30-day observation window: 7 days of observed history at the previous scan, 8 at this one. The score rises as the window fills, whether or not the server changes.
- 6 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.
- 4 Sept 26 +1
No change was recorded against any check on this day. Stability & Change Management went from 7 to 10. That category is still filling its 30-day observation window: 2 days of observed history at the previous scan, 3 at this one. The score rises as the window fills, whether or not the server changes.
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://numeral.usefulapi.io/mcp
TLS valid
Negotiated TLS 1.3 with TLS_AES_128_GCM_SHA256 .
| Subject | Issuer | Valid from | Valid until | Key | Signature | Serial |
|---|---|---|---|---|---|---|
| CN=usefulapi.io | CN=WE1,O=Google Trust Services,C=US | 16 Sept 2026 | 15 Dec 2026 | ECDSA 256 | ECDSA-SHA256 | bdf3e3b12ea314760e43eedc6db7d958 |
| SANs: usefulapi.io, numeral.usefulapi.io, *.numeral.usefulapi.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 numeral.usefulapi.io. — Not signed
| Zone | DS | Keys | Algorithms | Outcome |
|---|---|---|---|---|
| . | trust_anchor | 20326, 38696 | 8, 8 | Verified |
| io. | present | 57355 | 8 | Verified |
| usefulapi.io. | absent | Unsigned (proven) parent-signed NSEC/NSEC3 proves an unsigned delegation |
Authentication Enforced and verified
The endpoint asked for a token and published valid RFC 9728 metadata describing how to get one.
| Result | Enforced and verified |
|---|---|
| Enforced | On tool calls |
| HTTP status | 200 |
WWW-Authenticate challenge Bearer realm="OAuth", resource_metadata="https://numeral.usefulapi.io/.well-known/oauth-protected-resource/mcp", error="invalid_token", error_description="Missing or invalid access token"
Bearer realm="OAuth", resource_metadata="https://numeral.usefulapi.io/.well-known/oauth-protected-resource/mcp", error="invalid_token", error_description="Missing or invalid access token"Protected resource metadata
| Document | https://numeral.usefulapi.io/.well-known/oauth-protected-resource/mcp |
|---|---|
| Retrieved | Yes |
| Resource | https://numeral.usefulapi.io/mcp |
| Authorisation server | https://numeral.usefulapi.io |
Background: How OAuth 2.1 works in the 2026 MCP spec →
Transports 2 probes
| Transport | URL | Outcome | Status | Location |
|---|---|---|---|---|
| streamable-http | https://numeral.usefulapi.io/mcp | Verified | 200 | |
| http (plaintext) | http://numeral.usefulapi.io/mcp | Inconclusive | 401 |
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 →
numeral_calculate_tax Calculate tax ~170
Calculate sales tax / VAT for an order — a STATELESS quote that persists nothing (record it later with numeral_create_transaction using the returned calculation id). Returns per-jurisdiction rates, total_tax_amount, and totals. Provide a customer address and one or more line items (each needs reference_product_id OR product_category). Amounts are in the currency's smallest unit (cents). Numeral: POST /tax/calculations.
| Name | Type | Req | Description |
|---|---|---|---|
| customer | object | yes | Customer details — address is required. |
| metadata | object | – | Arbitrary string key/value metadata. |
| order_details | object | yes | Order details. |
| origin_address | object | – | The address a product ships from. Optional on 2024-09-01; required on API version 2025-05-12+. |
No output schema declared.
No examples provided.
numeral_create_customer Create customer ~99
CREATES a customer record — this WRITES to your Numeral customer list (used for order tracking and tax exemptions). Numeral: POST /tax/customers.
| Name | Type | Req | Description |
|---|---|---|---|
| string | yes | Customer email (required). | |
| is_tax_exempt | boolean | – | Whether this customer is tax exempt. |
| name | string | – | Customer name. |
| reference_customer_id | string | – | Your own id for this customer (for reference-based lookups). |
No output schema declared.
No examples provided.
numeral_create_product Create product ~112
CREATES (or upserts) a product with its tax category — this WRITES to your Numeral product catalog, which drives future tax calculations. Numeral: POST /tax/products.
| Name | Type | Req | Description |
|---|---|---|---|
| product_category | string | yes | A tax category from Numeral's taxonomy, e.g. "GENERAL_MERCHANDISE", "SAAS_GENERAL". |
| reference_product_id | string | yes | Your product id (used to reference this product in calculations). |
| reference_product_name | string | yes | Human-readable product name. |
No output schema declared.
No examples provided.
numeral_create_refund Create refund ~155
RECORDS a refund against a transaction — this WRITES a live tax/compliance record (adjusts tax owed). Use type="full" to refund the whole transaction, or type="partial" with line_items (each keyed by reference_product_id) for a partial refund. Numeral: POST /tax/refunds.
| Name | Type | Req | Description |
|---|---|---|---|
| line_items | array | – | Required for type="partial": the line items to refund. |
| refund_processed_at | number | – | Unix timestamp (SECONDS) the refund was made. Defaults to now if omitted. |
| transaction_id | string | yes | The transaction id (tr_...) to refund. |
| type | string | yes | "full" refunds the whole transaction; "partial" requires line_items. |
No output schema declared.
No examples provided.
numeral_create_transaction Create transaction ~137
RECORDS a completed sale as a transaction — this WRITES a live tax/compliance record used for filings. Supply the `calculation_id` returned by numeral_calculate_tax and your `reference_order_id`. Numeral: POST /tax/transactions.
| Name | Type | Req | Description |
|---|---|---|---|
| calculation_id | string | yes | The calculation id returned by numeral_calculate_tax. |
| metadata | object | – | Arbitrary string key/value metadata. |
| reference_order_id | string | yes | Your order id for this sale (used for record keeping / dedupe). |
| transaction_processed_at | number | – | Unix timestamp (SECONDS) the sale was processed. Defaults to now if omitted. |
No output schema declared.
No examples provided.
numeral_get_customer Get customer ~124
Get a customer by id. By default `customer_id` is the Numeral id (cus_...); set id_type to "reference" to look up by your own reference_customer_id. Returns name, email, and tax-exempt status. Numeral: GET /tax/customers/{customer_id}.
| Name | Type | Req | Description |
|---|---|---|---|
| customer_id | string | yes | The customer id — a Numeral id (cus_...) by default, or your reference id when id_type="reference". |
| id_type | string | – | Which id space `customer_id` is in (default: numeral). |
No output schema declared.
No examples provided.
numeral_get_product Get product ~69
Get a single product by its reference_product_id (your id). Returns the product's name, product_category, and timestamps. Numeral: GET /tax/products/{reference_product_id}.
| Name | Type | Req | Description |
|---|---|---|---|
| reference_product_id | string | yes | Your product id (the reference_product_id used when the product was created). |
No output schema declared.
No examples provided.
numeral_get_transaction Get transaction ~64
Get a recorded transaction by its Numeral id (tr_...). Returns the transaction with its line items, currencies, and metadata. Numeral: GET /tax/transactions/{transaction_id}.
| Name | Type | Req | Description |
|---|---|---|---|
| transaction_id | string | yes | The Numeral transaction id (tr_...). |
No output schema declared.
No examples provided.
numeral_list_products List products ~84
List your Numeral products (up to 50 per page), each with its reference id, name, and product_category. Use `cursor` (the last_product_id from a previous page) to paginate; has_more indicates more pages. Numeral: GET /tax/products.
| Name | Type | Req | Description |
|---|---|---|---|
| cursor | string | – | Pagination cursor — pass the last_product_id from the previous page. |
No output schema declared.
No examples provided.
numeral_list_transaction_refunds List transaction refunds ~58
List all refunds recorded against a transaction. Returns {refunds:[...]}. Numeral: GET /tax/transactions/{transaction_id}/refunds.
| Name | Type | Req | Description |
|---|---|---|---|
| transaction_id | string | yes | The Numeral transaction id (tr_...). |
No output schema declared.
No examples provided.
numeral_ping Ping (health check) ~41
Health check — verifies the API key works and reports the environment (test/prod), api_version, and server timestamp. Numeral: GET /tax/ping.
Input schema present but exposes no named parameters.
No output schema declared.
No examples provided.
What is the io.usefulapi/numeral MCP server?
io.usefulapi/numeral is an MCP server listed in the public MCP registry as io.usefulapi/numeral. Calculate sales tax & VAT, record transactions and refunds, manage products and customers. This page covers its hosted endpoint (https://numeral.usefulapi.io/mcp).
Is the io.usefulapi/numeral MCP server safe to use?
io.usefulapi/numeral scores 81 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 io.usefulapi/numeral MCP server expose?
io.usefulapi/numeral exposes 11 tools: numeral_ping, numeral_calculate_tax, numeral_get_transaction, numeral_list_transaction_refunds, numeral_list_products, and 6 more. Their descriptions and schemas cost roughly 1,113 tokens of context every time the server is loaded.
Does the io.usefulapi/numeral MCP server require authentication?
Yes. io.usefulapi/numeral asked us for credentials when we connected, so you will need to authorise it in your MCP client before it can do anything.
Is the io.usefulapi/numeral MCP server still maintained?
io.usefulapi/numeral 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.