Ranked by the provider's API Evangelist rating — the Kin Score is scored per provider, not per API, so every API of a provider shares its band. How the rating works →

Exemplar 23 Complete, well-documented, and agent-ready

CData Open APIThe Open API API from CData — 1 operation(s) for open api.82.9 Arazzo Specification (Redocly Tooling)Arazzo is the OpenAPI Initiative's specification for describing multi-step API workflows; Redocly is a prim...81.1 Redocly CLIRedocly CLI is an open-source command-line tool for working with OpenAPI descriptions, developer portals, a...81.1 Redocly RedocRedoc is the open-source engine that renders API reference documentation from OpenAPI definitions with a th...81.1 Snyk Open APIThe OpenAPI specification for this service.79.1 Stoplight CLIThe Stoplight CLI enables programmatic linting of API descriptions and pushing analysis results to the Stop...74.8 Stoplight ElementsElements is an open-source toolkit for building beautiful, interactive API documentation from OpenAPI speci...74.8 Stoplight PlatformStoplight Platform is a SaaS collaborative API design and documentation management tool providing a visual ...74.8 Stoplight PrismPrism is an open-source HTTP mock and proxy server that turns any OpenAPI v2/v3 or Postman Collection file ...74.8 Stoplight SpectralSpectral is an open-source JSON and YAML linter for creating automated API style guides and governance rule...74.8 Stoplight StudioStoplight Studio is the visual API design and technical writing editor included in the Stoplight Platform. ...74.8 Tvarka Sign APIMachine channel for Tvarka Sign: post a document and a list of signers and Tvarka runs its ordinary qualifi...70.9 Clerk OpenAPI SpecificationsPublic repository of OpenAPI specifications for Clerk's APIs, used as the source for generated SDKs and doc...70.5 Scalar API ClientScalar API Client is a fully open-source, offline-first REST API client built on the OpenAPI standard. Supp...70.3 Scalar API ReferencesScalar API References renders modern, interactive API documentation from OpenAPI and Swagger specifications...70.3 Scalar CLIThe Scalar CLI is a command-line interface for managing OpenAPI files, generating documentation, running mo...70.3 Scalar RegistryScalar Registry provides centralized management and versioning of OpenAPI Documents, JSON Schemas, and Spec...70.3 Act! Web APIJSON-based REST API for the Act! CRM database exposing contacts, companies, groups, opportunities, tasks, a...70.0 Power Platform Connectors APIAPI for custom and certified connectors that extend Power Platform capabilities across Power Apps, Power Au...69.7 Journey Planner (GraphQL)Core journey planning service built on OpenTripPlanner, providing departure boards for individual stops and...69.6 Mobility (GraphQL)Aggregation service for shared mobility data in Norway: real-time information about shared bikes, e-scooter...69.6 Vehicle Positions (GraphQL)GraphQL service providing real-time positions and status for public transport vehicles across Norway, inclu...69.6 Agorapulse Open APIThe Open API API from Agorapulse — 0 operation(s) for open api.68.2

Strong 25 Solid coverage with minor gaps

Speakeasy Contract TestingAPI contract test generation using OpenAPI specs and the Arazzo specification. Generates both test code and...66.3 Speakeasy DocsMDGenerate beautiful API documentation from OpenAPI specs. Automatic synchronization keeps docs current with ...66.3 Speakeasy MCP Server GenerationGenerate production-ready MCP server code from OpenAPI specifications. Deploy on your own infrastructure, c...66.3 Speakeasy SDK GenerationGenerate idiomatic, type-safe SDKs in 7+ languages from OpenAPI specs. Supports TypeScript, Python, Go, Jav...66.3 Speakeasy Terraform GenerationTurn your OpenAPI spec into a production-ready Terraform provider without the manual work. Automatically ke...66.3 Zuplo Open APIThe Open API API from Zuplo — 1 operation(s) for open api.65.7 StayingAPI Agent SkillsPublished portable SKILL.md agent skill in the stayingapi/travel-skills GitHub repo, referenced from the SD...64.9 StayingAPI MCP ServerHosted MCP server (Streamable HTTP, OAuth 2.1/PKCE) exposing 7 read-only tools mapping 1:1 to the REST endp...64.9 Treblle API DocumentationTreblle API Documentation automatically generates real-time API documentation from live API traffic and SDK...62.6 Treblle API InsightsTreblle API Insights is a free governance tool that evaluates OpenAPI specifications, providing scores from...62.6 APIMatic API Transformer APIAPIMatic API Transformer converts API definition files between more than 15 supported API specification for...61.6 Agent Disco Open APIOpenAPI60.9 APIVerve GraphQL API (alpha)Single GraphQL endpoint that fans out to multiple APIs in one request. Explicitly labeled alpha / not for p...60.9 APIVerve MCP ServerHosted remote MCP server (streamable HTTP) exposing every catalog endpoint as individual MCP tools with inp...60.9 Cisco Intersight Open APIThe Open API API from Cisco Intersight — 10 operation(s) for open api.60.3 GitBook Open APIThe OpenAPI endpoints let you integrate your existing or newly generated OpenAPI definitions into GitBook. ...60.2 Onshape Open APIGet the OpenAPI specification for the Onshape API.59.8 IBM WebSphere Open APIMicroProfile OpenAPI documentation endpoints58.4 ReefAPI MCP ServerHosted MCP server over streamable-HTTP with 5 discovery-first tools (search_engines, get_catalog, get_engin...57.8 DeveloperHub Documentation PlatformDeveloperHub provides a hosted platform for creating developer documentation including API references auto-...56.0 DEV Community Open APIThe Open API API from DEV Community — 1 operation(s) for open api.55.9 Windmill Open APIThe Open API API from Windmill — 2 operation(s) for open api.55.9 Bloomberg BLPAPI CoreThe Bloomberg Open API (BLPAPI) Core — the foundational service-oriented, socket-based API used by the Desk...54.8 Corva Data APIThe Corva Data API serves the records stored in Corva datasets — one-second operational data, engineering c...54.8 Custom Connectors APICustom connectors allow you to create wrappers around REST or SOAP APIs for use in Power Apps, Power Automa...54.3

Developing 23 Usable, with meaningful gaps to close

Truepill Open APIThe Open Api API from Truepill — 2 operation(s) for open api.53.4 iGaming Tools MCP ServerFree public hosted MCP server (Streamable HTTP, no API key, read-only, not metered) exposing the same iGami...52.7 Arazzo EngineOpen-source Python engine that executes Arazzo workflow specifications alongside OpenAPI operation definiti...52.2 VMware Cloud Director OpenAPIModern RESTful API for VMware Cloud Director defined using OpenAPI standards providing cloud service delive...51.3 NetScaler Next-Gen APINetScaler Next-Gen API is a modern declarative RESTful API built on the OpenAPI 3.0 specification that allo...50.9 Spec Scoring APIPublic, no-auth REST API for scoring OpenAPI documents. GET /api/review/checks returns the full set of chec...50.6 Dream Sports Open APIThe Open API API from Dream Sports — 1 operation(s) for open api.50.3 APIContext Open APIOpenAPI validation50.1 MuleSoft Anypoint Design Center APIThe Anypoint Design Center API provides access to the MuleSoft web-based API design environment for creatin...49.7 Stainless Open APIThe Open API API from Stainless — 1 operation(s) for open api.49.5 Zilla MCP GatewayThe Zilla MCP Gateway is the AI-facing face of the Zilla engine. It terminates Model Context Protocol Strea...48.6 Loa Healthcare Pricing MCP ServerHosted/remote MCP server 'LOA Healthcare Pricing' v1.0.0 over Streamable HTTP with 12 tools for CPT search,...47.0 3GPP Forge APIThe 3GPP Forge (forge.3gpp.org) is a self-managed GitLab instance where 3GPP publishes the machine-readable...46.3 Liblab MCP GeneratorGenerates a complete Model Context Protocol (MCP) server from an OpenAPI, Swagger, or Postman spec so AI ch...46.1 Liblab Open APIThe Open API API from Liblab — 2 operation(s) for open api.46.1 Liblab SDK GeneratorCloud-based generator that produces customizable, type-safe SDKs in seven target stacks (TypeScript, Python...46.1 Piknik.Spot Open APIThe Open API API from Piknik.Spot — 2 operation(s) for open api.45.9 KiotaKiota generates strongly-typed, lightweight API clients from OpenAPI descriptions in C#, Dart, Go, Java, PH...45.0 Ignition Gateway REST APIThe Ignition Gateway REST API (available in Ignition 8.3+) provides an OpenAPI- compliant HTTP interface to...43.9 Weidmüller Open APIAPI for reading the OpenAPI specification43.6 Hey API Openapi-Ts@hey-api/openapi-ts is an OpenAPI to TypeScript code generator that emits production-grade SDKs, types, val...41.5 Trieve REST APIProduction REST API for Trieve Cloud. Organizes resources around organizations, datasets, chunks, chunk gro...40.2 Twenty Open APIOpenAPI schema discovery39.5

Thin 25 Limited public surface area

Casey's General Stores Open APIThe Open API API from Casey's General Stores — 2 operation(s) for open api.38.1 Kareo Clinical Open APIThe Kareo Clinical Open API provides REST-based access to EHR clinical data, exposing patient clinical reco...37.3 Restate Open APIThe Open API API from Restate — 1 operation(s) for open api.36.4 OgenThe ogen code generator. Invoked as a build-time CLI against a local OpenAPI v3 document — `ogen [options] ...36.2 OWASP ZAP Open APIThe Open API API from OWASP ZAP — 2 operation(s) for open api.36.2 AutoRest CoreThe AutoRest Core package (@autorest/core) is the central engine that orchestrates code generation from Ope...34.7 Ambassador Blackbird API Development PlatformBlackbird is an API development platform that helps developers design, build, test, and manage APIs with AI...34.3 Ambassador Edge Stack Developer PortalThe Ambassador Edge Stack Developer Portal automatically detects and publishes API documentation, serving a...34.3 RefitterRefitter is a .NET source generator and CLI tool that produces Refit HTTP client interfaces from OpenAPI 2....34.1 Vert.x OpenAPIVert.x OpenAPI provides OpenAPI 3.1 specification support for Vert.x, enabling contract-driven API developm...31.9 Oapi-CodegenCommand-line tool and Go library that converts OpenAPI 3.0 and 3.1 specifications into Go server-side, clie...31.5 Xano Generated User APIsThe REST APIs that Xano users build visually. Each API group is served at its own /api:{token} path on the ...30.9 Apicurio CodegenApicurio Codegen generates Java JAX-RS server stubs and client code from OpenAPI specifications, enabling d...30.8 Apicurio Data ModelsApicurio Data Models is a Java and TypeScript library for parsing, validating, and manipulating OpenAPI and...30.8 Apicurio RegistryApicurio Registry is a high-performance, runtime registry for schemas and API designs. It stores and manage...30.8 Apicurio StudioApicurio Studio is a visual, zero-code API design tool for creating and editing OpenAPI and AsyncAPI specif...30.8 SchemathesisSchemathesis is a property-based API testing tool that automatically generates test cases from OpenAPI and ...30.4 NASA Earthdata Open APIThe Open API API from NASA Earthdata — 1 operation(s) for open api.30.3 UNIverse Research Information System APIThe REST backend of UNIverse (universe.unibas.ch), the University of Basel's research information system, a...29.9 TypeSpec OpenAPI EmitterThe TypeSpec OpenAPI emitter converts TypeSpec definitions to OpenAPI 3.0 specifications. It supports HTTP ...29.7 Mosaic Open APIThe Mosaic Open API exposes the workforce, project, and financial data Mosaic manages so firms can build cu...29.0 Hanyang University Open API Developer CenterHanyang University's own Open API platform, built and run by the university rather than bought from a vendo...27.7 Lumen OpenAPI Services (Level 3 legacy)The Level 3 / Lumen OpenAPI Services portal provided OpenAPI-described REST services such as the Lumen Loca...27.7 Quarkus Open APIThe Open API API from Quarkus — 2 operation(s) for open api.27.3 LayerZero Open APIThe Open API API from LayerZero — 1 operation(s) for open api.26.8

Emerging 35 Early or largely undocumented

42Crunch API Security AuditThe 42Crunch API Security Audit performs automated static analysis of API definitions (OpenAPI 2, 3.0, 3.1 ...26.0 Kubescape In-Cluster Component API (Open Source)The open-source Kubescape Operator's in-cluster components (storage, kubevuln, gateway, operator, node-agen...26.0 Morgan Stanley API Platform (REST)The institutional REST APIs on the Morgan Stanley API Platform let onboarded clients and third-party partne...26.0 Sourcegraph REST APIVersioned external REST API introduced in Sourcegraph 7.0 and intended as the stable integration surface go...26.0 Filecoin HTTP REST APIOpenAPI-specified HTTP REST interface for Filecoin nodes, covering chain resources (tipsets, blocks, execut...25.6 ReDocReDoc is an open-source API documentation renderer for OpenAPI specifications, originally created by Rebill...25.3 Open Charge Map Open APIThe Open API API from Open Charge Map — 1 operation(s) for open api.24.7 NSwagNSwag is an open source .NET toolchain for generating C# and TypeScript API clients and Swagger/OpenAPI spe...24.5 what3words API Docs and OpenAPI RepositoryPublic repository hosting the OpenAPI specification, LLM files, and reference material for the what3words P...24.2 Helidon Open APIThe Open API API from Helidon — 1 operation(s) for open api.22.9 Chainguard Unified API SpecThe unified Chainguard API specification combines API v1 and v2 definitions in a single reference, useful f...22.8 NEXON Open APIProgrammatic access to per-game data (character, ranking, match, and metadata) for Nexon titles. Authentica...22.4 Coupang Open APIThe Coupang Open API is a RESTful seller (vendor) API for managing the full marketplace lifecycle including...22.0 VacuumVacuum is the world's fastest OpenAPI linter written in Go. It processes API specifications at lightning sp...21.6 SpectralSpectral is a flexible JSON/YAML linter and style guide enforcer with built-in support for OpenAPI (v3.1, v...20.5 Optic CLIThe Optic CLI provides OpenAPI diffing, linting and breaking-change detection from the command line, compar...19.7 Flotiq APIAuto-generated RESTful and GraphQL APIs derived from user-defined content type definitions, enabling full C...19.2 FastMCP OpenAPI and FastAPI IntegrationFastMCP can generate an MCP server directly from an existing OpenAPI 3.x description or a FastAPI applicati...18.2 DreddDredd is a language-agnostic command-line tool for validating an API description document against a backend...17.7 OpenAPI VersioningOpenAPI handles versioning through the info.version field (using SemVer), the deprecated flag on individual...17.4 FastAPI FrameworkModern, fast web framework for building APIs with Python based on standard Python type hints.16.7 ISO 20022 API Resources CatalogueThe ISO 20022 API Resources Catalogue, governed by the API Standards Evaluation Group (APISEG), provides re...16.4 OpenAPI SpecificationThe OpenAPI Specification (OAS) defines a standard, language-agnostic interface to RESTful APIs which allow...16.3 OpenAPI SpecificationThe OpenAPI Specification (OAS) defines a standard, programming language-agnostic interface description for...15.5 SpecLynxStop wrestling with OpenAPI specs. SpecLynx OpenAPI Toolkit delivers the most effective way to author and m...15.3 SpecLynx ApiDOMA unified semantic parsing engine that underpins all SpecLynx products. ApiDOM parses OpenAPI, AsyncAPI, Ar...15.3 SpecLynx CLIA command-line interface for overlay operations, dereferencing, bundling, format conversion (JSON/YAML), an...15.3 SpecLynx EditorA browser-based OpenAPI editor with real-time validation, smart autocompletion, and live preview. No instal...15.3 SpecLynx Language ServiceAn LSP-compatible npm library (@speclynx/apidom-ls) providing 13 intelligent editing capabilities for API d...15.3 SpecLynx OpenAPI ToolkitA VS Code extension providing semantic editing, real-time validation, linting, and live preview for OpenAPI...15.3 DapperDoxDapperDox is an open-source API documentation generator that renders beautiful, customizable reference docs...14.9 LoopBackLoopBack is a highly extensible Node.js and TypeScript framework for building APIs and microservices with b...14.9 Connexion Python FrameworkConnexion is a contract-first Python web framework that loads an OpenAPI specification and routes requests ...13.1 JD Cloud OpenAPIJD Cloud OpenAPI is the programmatic control plane for JD Technology's public cloud — compute (VM), storage...12.7 PortmanPortman is an open source CLI tool that auto-generates Postman collections with contract and variation test...11.1

Minimal 4 Almost no public developer surface

API Insights AnalysisAPI Insights analyzes OpenAPI specifications (OAS v3, JSON or YAML) and produces detailed scorecards across...9.8 OasdiffOasdiff is an open-source tool for detecting breaking changes and generating changelogs from OpenAPI specif...8.5 FastAPIModern, fast web framework for building APIs with Python 3.7+.8.3 X-Road (Straumurinn) API CatalogueIceland's X-Road data-exchange layer (Straumurinn). Government-to-government REST services that publish Ope...7.6

Companies reaching this through an API (58)

These companies publish an API, specification or operation carrying “OpenAPI” but do not classify their business under it. Listed unranked and kept out of the count above, because one tagged operation is not a statement about what a company does.

Act! CRM Agent Disco Agorapulse Aklivity Ambassador APIContext Bloomberg CData CenturyLink (Lumen Technologies) Chainguard Cisco Intersight Citrix NetScaler Corva AI DEV Community Dream Sports Entur FastMCP Filecoin Flotiq GitBook Helidon IBM WebSphere Inductive Automation ISO 20022 Kareo Kubescape LayerZero Microsoft Power Apps Microsoft Power Platform APIs Morgan Stanley Mosaic MuleSoft NASA Earthdata Onshape Open Charge Map OpenAPI OpenJS Foundation OWASP ZAP Piknik.Spot Python Standard Library and Popular Quarkus REST Restate Snyk Sourcegraph Treblle Trieve Truepill Twenty University of Basel

Show all 58 companies ↓

Versioning Protocols Vert.x VMware Weidmüller what3words Windmill Xano Zuplo

Score breakdown

Frequency

66.4

log-scaled weighted occurrences

Breadth

3.4

spread across providers

Quality lift

44.7

mean composite of providers using it

Cohesion

9.6

strength of nearest seed neighbor

Where this tag comes from

Provider tag152

Api tag135

Openapi tag26

Openapi op tag43

Cohort brief

Auto-generated

The 149 providers in the APIs.io catalog tagged OpenAPI, scored on the Kin Score. Every figure below is computed from the catalog — nothing here is written.

Providers

149

of 151 in the catalog

Mean Kin Score

43.1

+20.9 vs catalog 22.2

Mean Agent Readiness

29.7

+17.7 vs catalog 12

Spread

7.6–93.8

median 42.7 · σ 18.1

How the 149 split by band

Exemplar 13Strong 32Developing 38Thin 35Emerging 27Minimal 4

Facet averages, against the whole catalog

Facet	This cohort	Catalog	Difference	Scored
Developer Ergonomics	47.5	23.2	+24.3	149
Contract Quality	41.3	17.2	+24.1	149
Operational Transparency	33.9	13	+20.9	149
Access Clarity	40	23.9	+16.1	149
Contract Governance	17.4	6.5	+10.9	149
Discoverability	67.9	57.9	+10	149

A facet is averaged over the members that carry it, not over the whole cohort — the “Scored” column is that count. Averaging an absent facet as zero would score our own coverage gaps as the providers’ posture.

What this cohort publishes

Artifact	This cohort	Catalog	Difference
MCP server (any)	40%	13%	+27
MCP server (first-party)	42%	12%	+30
Agent Skills	0%	0%	0
OAuth scopes	21%	11%	+10
Security	97%	98%	-1
Arazzo workflows	5%	2%	+3
Governance rules	35%	16%	+19

mcp_pct counts any mcp/ artifact including ones API Evangelist derived from the provider OpenAPI; mcp_first_party_pct counts only servers the provider publishes. Prefer the latter.

Top by Kin Score

1 APIs.io 93.8
2 Zoho CRM 84.4
3 Redocly 81.1
4 OpenMercantil 79
5 Postman 78
6 Stoplight 74.8
7 0xArchive 71.7
8 Cvent Event Cloud 70.9
9 Tvarka ATK API 70.9
10 Scalar 70.3

Work with this as data

Every tag 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 tags

7 MCP tools reach this

find_tagsBrowse and filter every tag in the catalog.
get_cohortThis tag as a scored cohort — every provider carrying it, with scores.
cohort_statsPRO — the distribution across this tag: mean, median, band split, adoption rates.
cohort_rankingsPRO — the leaderboard, on composite AND agent-readiness axes.
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 tag

curl "https://apis.io/api/v1/tags/openapi"

All tags

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

As a scored cohort

curl "https://apis.io/api/v1/cohorts/tag/openapi"

The distribution (Pro)

curl "https://apis.io/api/v1/cohorts/tag/openapi/stats" \
  -H "X-API-Key: $APIS_IO_KEY"

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

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OpenAPI

Providers using this tag (150)

APIs with this tag (135)