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Head to head · Tax calculate · October 2026 research run

Kintsugi vs Numeral

Kintsugi scores 60.7 (C) on agent readiness against Numeral's 49.3 (D), and leads in 6 of 7 scored categories. Both do tax calculate.

KintsugiKintsugi AI, Inc. · HTTP API C60.7/100#392 of 722 NumeralNumeral Two, Inc. · HTTP API D49.3/100#611 of 722

Which one, for what

Kintsugi C

Good for An agent working for a seller that already has Kintsugi Premium and wants estimates, transaction sync, exemptions, nexus, registrations and filing status through one API, or read-only answers about an account through the OAuth MCP server.

Ahead on

  • Reliability, 73 against 25
  • Security & auth, 52 against 47
  • Maintenance & community, 78 against 60
  • Transparency & trust, 60 against 45

Watch for

API access, SDKs and real-time tax calculation are listed only under Premium, which is priced on request. API keys need a paid plan that includes them

Numeral D

Good for An agent working for a seller or platform that has a Numeral account and needs tax at checkout, committed transactions for filing, and read access to nexus, registrations and filings through MCP.

Also in its favour

  • No incidents deducted, where Kintsugi loses 3 points for them

Watch for

No status page, uptime SLA or numeric rate limit was found. The product page says rate limits can be removed on request

Score by category

CategoryWeight this runKintsugiNumeralEdge
Reliability16%207325Kintsugi +48
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.28787even
Agent ergonomics13%16.27571Kintsugi +4
Security & auth14%17.55247Kintsugi +5
Payments & pricing10%12.51310Kintsugi +3
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87860Kintsugi +18
Transparency & trust7%8.86045Kintsugi +15
Negative events≤15-30
Total60.7 · C49.3 · D

Facts side by side

FactKintsugiNumeral
KindHTTP APIHTTP API
VendorKintsugi AI, Inc.Numeral Two, Inc.
Hosted endpointhttps://api.trykintsugi.comhttps://api.numeralhq.com
TransportsHTTP, Streamable HTTPHTTP, Streamable HTTP
AuthOAuth or keyAPI key
PricingPaidPaid
x402nono
LicenceProprietary service under the Kintsugi Terms of Service. The Python SDK repository is MITProprietary service under Numeral's terms of service. The Go, Python and Node SDKs are Apache-2.0
Tools exposed5514
Read-only variant documentedyesyes
llms.txtyesyes
Last release2026-10-072026-09-15
Terms last updated2026-09-29no date given
Privacy policy last updated2025-04-13no document linked
Customer content may train modelsyesnot found in the text
Terms restrict automated accessyesnot found in the text
Terms restrict benchmarkingyesnot found in the text
Terms or service can change without noticenot found in the textnot found in the text
Arbitration or class-action waiveryesyes
Popularity71 npm/wk, 10 PyPI/wk0 stars, 9 npm/wk, 19 PyPI/wk

Verdicts

Kintsugi

The docs are built for machine readers, with llms.txt, Markdown pages, a public OpenAPI 3.1 file, a dated changelog and an MCP server whose 55 tools carry read-only and destructive annotations. API keys need the custom-priced Premium plan and carry no scopes, no general rate limit is published, and breaking changes reached the pinned 2026-07-21 release in October 2026.

Numeral

Docs are written for agents, with a public OpenAPI spec for 32 operations, Markdown pages, llms.txt and a remote MCP server whose 14 tools are read-only by default. No status page, numeric rate limit or SLA was found, the API ignores idempotency keys, and API access is sold on a custom plan after a demo.

Before you call either

Kintsugi

  1. Send Api-Key and pin Api-Version (for example 2026-10-06) on Tenanted API calls to https://api.trykintsugi.com. Without the header a request runs against 2026-07-21
  2. Use x-api-key and x-organization-id with /v1 paths for the SDKs and the docs MCP server. They don't cover the Tenanted API
  3. Call POST /tax-estimations for a quote. Nothing is stored. Record the sale with a transaction create, which answers 202, then check processingStatus before reading tax totals
  4. Always send externalId on creates. A repeat with the same externalId and source returns the stored record with 200 and doesn't apply the new fields
  5. Branch on the error code, not the message. Retry 429, 500 and 503 with exponential backoff, and restart paging from the first page on stale_cursor

Numeral

  1. Send X-API-Version: 2026-03-01 on every call to https://api.numeralhq.com. Merchant, platform and certificate endpoints reject requests without it
  2. Commit with a stable reference_order_id. On REFERENCE_ORDER_ID_ALREADY_EXISTS look up the existing transaction, because Idempotency-Key is ignored
  3. Commit before the calculation's expires_at. If it has expired, calculate again and commit the new calculation_id with the original reference_order_id
  4. Send amount as the line total in minor units to /tax/calculations and as the per-unit price to /tax/platform/calculations
  5. Start with an sk_test_ key. Certificate endpoints and MCP certificate tools are live only and answer TESTMODE_NOT_SUPPORTED or live_mode_required

Questions

Which is better for AI agents, Kintsugi or Numeral?

Kintsugi scores 60.7 (C) on agent readiness against Numeral's 49.3 (D), and leads in 6 of 7 scored categories.

Do Kintsugi and Numeral need an API key?

Kintsugi takes an API key or an OAuth sign-in. Numeral needs an API key.

Can an agent call Kintsugi and Numeral without installing anything?

Yes. Kintsugi has a hosted endpoint at https://api.trykintsugi.com and Numeral at https://api.numeralhq.com.

Other comparisons with Kintsugi or Numeral

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