Napkin Math

Napkin Math is a personalized AI food journal from Paper Star (a Y Combinator company, founded 2026 in San Francisco by Manuel Castro, Claire Nord, and Jynnie Tang). Marketed as "an AI nutrition coach in your pocket," it is a simple, beautiful food diary that helps people log meals and understand their eating habits over time. The product is a consumer mobile application rather than a developer platform: as of this profile Napkin Math publishes no public API, developer documentation, SDKs, OpenAPI, MCP server, or /.well-known discovery surface. This entry is maintained in the API Evangelist network as a company profile and enrichment lead; it will be upgraded to carry API artifacts if and when Napkin Math or Paper Star exposes a public API surface.

Napkin Math is profiled on the APIs.io network. Tagged areas include Company, Nutrition, Food Journal, Health, and Diet.

🌐 Visit website 📡 Profile data on GitHub

8.8/100 minimal ▬ flat Agent 0/100 human only saas Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

0 APIs

Company NutritionFood JournalHealth Diet Artificial Intelligence Consumer Applications Mobile App iOS

Kin Score

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

Composite quality — 8.8/100 · minimal

Contract Quality 0.0 / 21

Developer Ergonomics 0.0 / 17

Access Clarity 3.6 / 17

Operational Transparency 0.0 / 11

Contract Governance 0.0 / 10

Discoverability 4.1 / 9

Regulatory Posture 1.5 / 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 Health 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/.

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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 0.0 — up to +20.0 composite points
Access Clarity scores 21.1 — up to +15.8 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/napkin-math/apis.yml: open an issue on github.com/api-evangelist/napkin-math 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 →

Markets this provider is in provisional

The Kin Score Market layer reads a provider inside its market: its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted: not part of the Kin Score or agent readiness.

Market	Position	Depth	Registered MCP server	Declares compatibility
Apple Accessory & Device Ecosystem (MFi, Matter, Apple partners)	undeclared	-	-	-
Mobile SDK Publishers (Play SDK Index, CocoaPods, ADA certification)	undeclared	-	-	-

Registered MCP server and declares compatibility are report only — not weighted. Undeclared means we found nothing we can read, so there is no number: we never infer integrations.

Security Posture 1

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

Napkin Math Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Resources

Access & Security 1

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Commercial 2

Pricing, plans, and the legal terms of use

TermsOfService

TermsOfService

PrivacyPolicy

PrivacyPolicy

Company 1

The organization behind the API

Website

Website

Source (apis.yml)

aid: napkin-math
name: Napkin Math
description: 'Napkin Math is a personalized AI food journal from Paper Star (a Y Combinator company, founded 2026 in San Francisco
  by Manuel Castro, Claire Nord, and Jynnie Tang). Marketed as "an AI nutrition coach in your pocket," it is a simple, beautiful
  food diary that helps people log meals and understand their eating habits over time. The product is a consumer mobile application
  rather than a developer platform: as of this profile Napkin Math publishes no public API, developer documentation, SDKs,
  OpenAPI, MCP server, or /.well-known discovery surface. This entry is maintained in the API Evangelist network as a company
  profile and enrichment lead; it will be upgraded to carry API artifacts if and when Napkin Math or Paper Star exposes a
  public API surface.'
deliveryModel:
  model: saas
  open_source: false
  commercial: true
  callable_host: false
  label: Hosted service · you call their endpoint
  confidence: medium
  source:
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source:
  - security
  generated: '2026-11-06'
  method: derived
image: https://napkinmath.club/opengraph-image.png
url: https://raw.githubusercontent.com/api-evangelist/napkin-math/refs/heads/main/apis.yml
x-type: company
x-source: vc-portfolio
x-backed-by:
- y-combinator
x-parent-company: Paper Star
x-tier: stub
x-tier-reason: consumer-app-no-api
specificationVersion: '0.23'
created: '2026-07-17'
modified: '2026-07-20'
tags:
- Company
- Nutrition
- Food Journal
- Health
- Diet
- Artificial Intelligence
- Consumer Applications
- Mobile App
- iOS
tags_raw:
- Company
- Nutrition
- Food Journal
- Health
- Diet
- Artificial Intelligence
- Consumer Application
- Mobile Application
- iOS
- Mobile Applications
common:
- url: https://napkinmath.club
  type: Website
- url: https://www.paperstar.cc/napkin-math/terms
  type: TermsOfService
- url: https://www.paperstar.cc/napkin-math/terms
  type: PrivacyPolicy
- url: security/napkin-math-domain-security.yml
  type: DomainSecurity
apis: []
x-enrichment:
  date: '2026-07-20'
  status: nochange
  artifacts_added: 0
  pass: local-v1
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io

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