Rational

Rational (rational.to) is a Y Combinator (S26) company building AI employees, or "AI coworkers," for accounting and finance teams. Its AI agents onboard themselves to a firm, build a company "brain," and perform recurring accounting work — accounts payable, AR collections, bookkeeping, bank reconciliation, document collection, expense review, and month-end close — while keeping postings, payment release, and policy-sensitive decisions behind explicit human approval gates with an inspectable review history. Founded in 2026 in San Francisco by Jibril Moinuddin and Christ Xu, Rational targets accounting firms and finance teams facing a structural capacity and labor shortage. As an early-stage company it currently exposes a marketing and agent-discovery surface (llms.txt, ai-discovery.json, RFC 9116 security.txt) rather than a public developer API; this profile captures that surface and will be enriched as a developer platform ships.

Rational is profiled on the APIs.io network. Tagged areas include Company, Artificial Intelligence, AI Agents, Accounting, and Finance.

Rational’s developer surface includes pricing, engineering blog, support, and 12 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

12.4/100 emerging ▬ flat Agent 0/100 human only Front door AI 3/6 light Heartbeat 94/100 alive Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessPaid

0 APIs

Company Artificial Intelligence AI Agents Accounting Finance Bookkeeping Accounts Payable Automation Fintech Y Combinator

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 12.4/100 · emerging

Contract Quality 0.0 / 21

Developer Ergonomics 0.4 / 17

Access Clarity 4.5 / 17

Operational Transparency 1.5 / 11

Contract Governance 0.0 / 10

Discoverability 4.7 / 9

Regulatory Posture 1.6 / 15

Agent readiness — 0/100 · human only

Machine-Readable Contract 0 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 0 / 10

Idempotency 0 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 0 / 7

Rate-Limit Signaling 0 / 7

Typed Event Surface 0 / 6

Agent Skills 0 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

Show this score on your site.

It updates itself when the score changes. Paste this where you link to your API docs:

<a href="https://apis.io/providers/rational/"><img src="https://apis.io/badge/rational/card.svg" alt="Rational on APIs.io — Kin Score by API Evangelist"></a>

Other styles, a README pill and a shields.io endpoint are on the badge page.

Raise your score.

Agent readiness — checks not met, largest first (exact, from this profile):

Machine-Readable Contract +18 pts — api_specs includes an OpenAPI document
MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey)
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented)
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes

13 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 0.0 — up to +25.0 composite points
Developer Ergonomics scores 2.4 — up to +19.5 composite points
Access Clarity scores 26.3 — up to +14.7 composite points

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/rational/apis.yml: open an issue on github.com/api-evangelist/rational to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

Rational API pricing

Prices published by Rational, read 2026-10-07 from rational.to/ai-accounting-pricing.html.

Plan	Price
For startups	Starting at $399/ month Includes: Monthly bookkeeping and financial statements; Human review and access to accounting support; Annual
For enterprises	Custom Includes: AP, AR and month-end close workflows; connections to existing accounting systems; permissions and hu

Plan details, limits and sources →

Pricing Plans 1

Published pricing tiers and plan structures.

Rational Plans Pricing

2 plans

PLANS

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Rational Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Rational Vulnerability Disclosure

security.txt · contact published

SECURITY

Resources

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

WellKnown

WellKnown

LLMsTxt

LLMsTxt

Build 1

SDKs, sample code, and the tooling you integrate with

GitHubOrganization

GitHubOrganization

Access & Security 5

Authentication, authorization, and security posture

VulnerabilityDisclosure

VulnerabilityDisclosure

DomainSecurity

SecurityPolicy

Security

SecurityTxt

Operate 1

Status, limits, changes, and where to get help

Support

Support

Commercial 2

Pricing, plans, and the legal terms of use

Pricing

Pricing

Plans

Plans

Company 3

The organization behind the API

Website

Website

Blog

Blog

BlogRSS

BlogRSS

Other 1

Properties that don't map to a standard resource type

Product

Product

Source (apis.yml)

aid: rational
name: Rational
description: Rational (rational.to) is a Y Combinator (S26) company building AI employees, or "AI coworkers," for accounting
  and finance teams. Its AI agents onboard themselves to a firm, build a company "brain," and perform recurring accounting
  work — accounts payable, AR collections, bookkeeping, bank reconciliation, document collection, expense review, and month-end
  close — while keeping postings, payment release, and policy-sensitive decisions behind explicit human approval gates with
  an inspectable review history. Founded in 2026 in San Francisco by Jibril Moinuddin and Christ Xu, Rational targets accounting
  firms and finance teams facing a structural capacity and labor shortage. As an early-stage company it currently exposes
  a marketing and agent-discovery surface (llms.txt, ai-discovery.json, RFC 9116 security.txt) rather than a public developer
  API; this profile captures that surface and will be enriched as a developer platform ships.
url: https://raw.githubusercontent.com/api-evangelist/rational/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- y-combinator
x-tier: stub
x-tier-reason: portfolio-lead
deliveryModel:
  model: unknown
  open_source: false
  commercial: false
  callable_host: false
  label: Delivery model not determined — needs a product licence on record
  confidence: low
  source:
  - none
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: paid
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Paid
  confidence: low
  source:
  - plans
  - security
  generated: '2026-11-06'
  method: derived
specificationVersion: '0.23'
created: '2026-07-17'
modified: '2026-07-20'
image: https://rational.to/favicon.png
tags:
- Company
- Artificial Intelligence
- AI Agents
- Accounting
- Finance
- Bookkeeping
- Accounts Payable
- Automation
- Fintech
- Y Combinator
apis: []
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: Pricing
  url: https://rational.to/ai-accounting-pricing.html
- type: Plans
  url: plans/rational-plans-pricing.yml
- type: VulnerabilityDisclosure
  url: security/rational-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/rational-domain-security.yml
- type: Website
  url: https://rational.to/
- type: Product
  url: https://rational.to/product.html
- type: Blog
  url: https://rational.to/blog.html
- type: BlogRSS
  url: https://rational.to/feed.xml
- type: Support
  url: https://rational.to/book-demo.html
- type: GitHubOrganization
  url: https://github.com/rational-to
- type: SecurityPolicy
  url: https://rational.to/security.html
- type: Security
  url: https://rational.to/security.html
- type: SecurityTxt
  url: well-known/rational-security.txt
- type: WellKnown
  url: well-known/rational-well-known.yml
- type: LLMsTxt
  url: llms/rational-llms.txt
x-enrichment:
  date: '2026-07-20'
  status: enriched
  artifacts_added: 6
  pass: local-v1

Rational API — frequently asked questions

How much does the Rational API cost?

Rational publishes its prices; its For startups plan is Starting at $399/ month as of 2026-10-07. APIs.io lists 2 pricing plans for Rational, with each plan's price, limits and inclusions under Pricing on this page.

Is the Rational API ready for AI agents?

Rational has a Kin Score of 12.4 out of 100 (emerging) and an Agent Readiness score of 0.0 (human-only), scored by API Evangelist on 2026-11-06.

Work with this as data

Every provider here is available over the APIs.io API and to AI agents over MCP.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for providers

9 MCP tools reach this

find_providersBrowse and filter every provider in the catalog.
get_provider_artifactsEvery artifact this provider publishes, grouped by type.
get_provider_operationsEvery operation across all of their OpenAPIs — one call instead of parsing every spec.
get_provider_toolsEvery MCP tool they ship, with the operation each wraps.
get_provider_evidenceHow each part of their score was established. Free — the basis for a claim should not sit behind it.
get_provider_ratingPRO — composite, band, trend and facet scores.
apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

All 92 tools →

Call it yourself

curl for this page

This provider

curl "https://apis.io/api/v1/providers/rational"

All providers

curl "https://apis.io/api/v1/providers?limit=25"

Every operation they expose

curl "https://apis.io/api/v1/providers/rational/operations?limit=25"

How their score was established

curl "https://apis.io/api/v1/providers/rational/evidence"

Calls without X-API-Key need no key. Calls with it need a paid plan — get a key.

Get an API key

Free tier, no form to fill in. Signing in shares your email address with us — we store it to create your key and to recognise you if you sign in with another provider. See our Privacy Policy and Terms.

GitHub Google LinkedIn

A second provider on the same verified email joins the account you already have.