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
10.1/100 minimal ▬ flat Agent 7/100 human only Full breakdown ↓
scored 2026-07-27 · rubric v0.5
0 APIs
CompanyArtificial IntelligenceAI AgentsAccountingFinanceBookkeepingAccounts PayableAutomationFintechY Combinator

Kin Score

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 10.1/100 · minimal
Contract Quality 0.0 / 25
Developer Ergonomics 1.3 / 20
Commercial Clarity 0.0 / 20
Operational Transparency 2.1 / 13
Governance 0.0 / 12
Discoverability 6.8 / 10
Agent readiness — 7/100 · human only
Machine-Readable Contract 0 / 18
Agentic Access Contract 0 / 15
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 4 / 4
Consent & Bot Identity 3 / 3
Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. 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. Want it done for you? Prioritized profiling — $2,500 →

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
DomainSecurity
 SecurityPolicy
SecurityPolicy
 Security
Security
 SecurityTxt
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)

apis.yml Raw ↑ 
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
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source: []
  generated: '2026-07-22'
  method: derived
specificationVersion: '0.20'
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