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 engineering blog, support, and 11 more developer resources.

🌐 Visit website 📡 Source on GitHub

6.6/100 minimal ▬ flat Agent 0/100 human only Full breakdown ↓
scored 2026-09-08 · rubric v0.20.0

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 2026-09-08 · rubric v0.20.0

Composite quality — 6.6/100 · minimal

Contract Quality 0.0 / 25

Developer Ergonomics 0.5 / 20

Access Clarity 0.0 / 20

Operational Transparency 0.3 / 13

Contract Governance 0.0 / 12

Discoverability 5.7 / 10

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

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.

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 github.com/api-evangelist/rational: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

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

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: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source: []
  generated: '2026-07-22'
  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: 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

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