Polymorph

Polymorph is a Y Combinator (Winter 2026) startup building adaptive consumer internet infrastructure that personalizes user experiences with AI agents. Founded in San Francisco by Andrew Sy, the platform runs thousands of continuous product and lifecycle-engagement experiments for its customers, each carrying the craft of that product's direction and brand, so consumer teams can scale experimentation in product surfaces without being bottlenecked by headcount or design capacity. Its stated vision is to make the consumer internet polymorphic — one that adapts to each user and optimizes for delightful experiences. As of this profile the company operates a marketing site only; it publishes no public API, developer documentation, SDKs, or developer portal.

Polymorph is profiled on the APIs.io network. Tagged areas include Company, Personalization, Experimentation, Consumer Internet, and Artificial Intelligence.

Polymorph’s developer surface includes legal docs, support, and 8 more developer resources.

🌐 Visit website 📡 Source on GitHub

11.5/100 emerging ▬ flat Agent 0/100 human only saas Full breakdown ↓
scored 2026-09-08 · rubric v0.20.0

0 APIs

Company Personalization Experimentation Consumer Internet Artificial Intelligence Machine-Learning Growth Y Combinator

Kin Score

Kin Score How this is scored →
scored 2026-09-08 · rubric v0.20.0

Composite quality — 11.5/100 · emerging

Contract Quality 0.0 / 25

Developer Ergonomics 1.0 / 20

Access Clarity 4.2 / 20

Operational Transparency 1.4 / 13

Contract Governance 0.0 / 12

Discoverability 5.0 / 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/polymorph: 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.

Polymorph Domain Security

TLSv1.3 · HSTS · DNSSEC · DMARC

SECURITY

Polymorph Vulnerability Disclosure

Hackerone · contact published

SECURITY

Resources

Access & Security 3

Authentication, authorization, and security posture

VulnerabilityDisclosure

VulnerabilityDisclosure

Security

Security

DomainSecurity

DomainSecurity

Operate 1

Status, limits, changes, and where to get help

Support

Support

Commercial 3

Pricing, plans, and the legal terms of use

TermsOfService

TermsOfService

PrivacyPolicy

PrivacyPolicy

Legal

Legal

Company 2

The organization behind the API

Website

Website

CrunchBase

CrunchBase

Other 1

Properties that don't map to a standard resource type

Y Combinator

Y Combinator

Source (apis.yml)

aid: polymorph
name: Polymorph
description: Polymorph is a Y Combinator (Winter 2026) startup building adaptive consumer internet infrastructure that personalizes
  user experiences with AI agents. Founded in San Francisco by Andrew Sy, the platform runs thousands of continuous product
  and lifecycle-engagement experiments for its customers, each carrying the craft of that product's direction and brand, so
  consumer teams can scale experimentation in product surfaces without being bottlenecked by headcount or design capacity.
  Its stated vision is to make the consumer internet polymorphic — one that adapts to each user and optimizes for delightful
  experiences. As of this profile the company operates a marketing site only; it publishes no public API, developer documentation,
  SDKs, or developer portal.
url: https://raw.githubusercontent.com/api-evangelist/polymorph/refs/heads/main/apis.yml
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: []
  generated: '2026-07-22'
  method: derived
image: https://usepolymorph.com/polymorph-mark.png
x-type: company
x-source: vc-portfolio
x-backed-by:
- techstars
- y-combinator
x-tier: stub
x-tier-reason: portfolio-lead
x-website-note: Original getpolymorph.com domain from the portfolio source now resolves to an unrelated gambling site; the
  live company site is usepolymorph.com (confirmed via the Y Combinator company page, YC W26).
specificationVersion: '0.23'
created: '2026-07-17'
modified: '2026-07-20'
tags:
- Company
- Personalization
- Experimentation
- Consumer Internet
- Artificial Intelligence
- Machine-Learning
- Growth
- Y Combinator
tags_raw:
- Company
- Personalization
- Experimentation
- Consumer Internet
- Artificial Intelligence
- Machine Learning
- Growth
- Y Combinator
apis: []
x-enrichment:
  date: '2026-07-20'
  status: minimal
  artifacts_added: 2
  pass: local-v1
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
common:
- type: Website
  url: https://usepolymorph.com/
- type: CrunchBase
  url: https://www.crunchbase.com/organization/polymorph-0146
- type: Y Combinator
  url: https://www.ycombinator.com/companies/polymorph
- type: TermsOfService
  url: https://usepolymorph.com/legal/terms
- type: PrivacyPolicy
  url: https://usepolymorph.com/legal/privacy
- type: Legal
  url: https://usepolymorph.com/legal
- type: Support
  url: mailto:founders@usepolymorph.com
- type: VulnerabilityDisclosure
  url: security/polymorph-vulnerability-disclosure.yml
- type: Security
  url: https://usepolymorph.com/legal/security
- type: DomainSecurity
  url: security/polymorph-domain-security.yml

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/polymorph"

All providers

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

Every operation they expose

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

How their score was established

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

Discovery needs no key. Ratings and market analysis are Pro.

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.