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 25 Complete, well-documented, and agent-ready

CData Open APIThe Open API API from CData — 1 operation(s) for open api.84.4 Arazzo Specification (Redocly Tooling)Arazzo is the OpenAPI Initiative's specification for describing multi-step API workflows; Redocly is a prim...82.6 Redocly CLIRedocly CLI is an open-source command-line tool for working with OpenAPI descriptions, developer portals, a...82.6 Redocly RedocRedoc is the open-source engine that renders API reference documentation from OpenAPI definitions with a th...82.6 Snyk Open APIThe OpenAPI specification for this service.80.6 Stoplight CLIThe Stoplight CLI enables programmatic linting of API descriptions and pushing analysis results to the Stop...71.8 Stoplight ElementsElements is an open-source toolkit for building beautiful, interactive API documentation from OpenAPI speci...71.8 Stoplight PlatformStoplight Platform is a SaaS collaborative API design and documentation management tool providing a visual ...71.8 Stoplight PrismPrism is an open-source HTTP mock and proxy server that turns any OpenAPI v2/v3 or Postman Collection file ...71.8 Stoplight SpectralSpectral is an open-source JSON and YAML linter for creating automated API style guides and governance rule...71.8 Stoplight StudioStoplight Studio is the visual API design and technical writing editor included in the Stoplight Platform. ...71.8 Scalar API ClientScalar API Client is a fully open-source, offline-first REST API client built on the OpenAPI standard. Supp...71.7 Scalar API ReferencesScalar API References renders modern, interactive API documentation from OpenAPI and Swagger specifications...71.7 Scalar CLIThe Scalar CLI is a command-line interface for managing OpenAPI files, generating documentation, running mo...71.7 Scalar RegistryScalar Registry provides centralized management and versioning of OpenAPI Documents, JSON Schemas, and Spec...71.7 Clerk OpenAPI SpecificationsPublic repository of OpenAPI specifications for Clerk's APIs, used as the source for generated SDKs and doc...71.4 Power Platform Connectors APIAPI for custom and certified connectors that extend Power Platform capabilities across Power Apps, Power Au...71.1 Tvarka Sign APIMachine channel for Tvarka Sign: post a document and a list of signers and Tvarka runs its ordinary qualifi...70.1 Act! Web APIJSON-based REST API for the Act! CRM database exposing contacts, companies, groups, opportunities, tasks, a...69.9 Agorapulse Open APIThe Open API API from Agorapulse — 0 operation(s) for open api.69.5 Speakeasy Contract TestingAPI contract test generation using OpenAPI specs and the Arazzo specification. Generates both test code and...67.6 Speakeasy DocsMDGenerate beautiful API documentation from OpenAPI specs. Automatic synchronization keeps docs current with ...67.6 Speakeasy MCP Server GenerationGenerate production-ready MCP server code from OpenAPI specifications. Deploy on your own infrastructure, c...67.6 Speakeasy SDK GenerationGenerate idiomatic, type-safe SDKs in 7+ languages from OpenAPI specs. Supports TypeScript, Python, Go, Jav...67.6 Speakeasy Terraform GenerationTurn your OpenAPI spec into a production-ready Terraform provider without the manual work. Automatically ke...67.6

Strong 18 Solid coverage with minor gaps

StayingAPI Agent SkillsPublished portable SKILL.md agent skill in the stayingapi/travel-skills GitHub repo, referenced from the SD...64.8 StayingAPI MCP ServerHosted MCP server (Streamable HTTP, OAuth 2.1/PKCE) exposing 7 read-only tools mapping 1:1 to the REST endp...64.8 Treblle API DocumentationTreblle API Documentation automatically generates real-time API documentation from live API traffic and SDK...63.2 Treblle API InsightsTreblle API Insights is a free governance tool that evaluates OpenAPI specifications, providing scores from...63.2 APIMatic API Transformer APIAPIMatic API Transformer converts API definition files between more than 15 supported API specification for...63.1 Zuplo Open APIThe Open API API from Zuplo — 1 operation(s) for open api.62.3 Windmill Open APIThe Open API API from Windmill — 2 operation(s) for open api.61.1 APIVerve GraphQL API (alpha)Single GraphQL endpoint that fans out to multiple APIs in one request. Explicitly labeled alpha / not for p...60.8 APIVerve MCP ServerHosted remote MCP server (streamable HTTP) exposing every catalog endpoint as individual MCP tools with inp...60.8 Cisco Intersight Open APIThe Open API API from Cisco Intersight — 10 operation(s) for open api.59.7 Onshape Open APIGet the OpenAPI specification for the Onshape API.59.7 IBM WebSphere Open APIMicroProfile OpenAPI documentation endpoints58.0 ReefAPI MCP ServerHosted MCP server over streamable-HTTP with 5 discovery-first tools (search_engines, get_catalog, get_engin...57.7 DeveloperHub Documentation PlatformDeveloperHub provides a hosted platform for creating developer documentation including API references auto-...57.5 Bloomberg BLPAPI CoreThe Bloomberg Open API (BLPAPI) Core — the foundational service-oriented, socket-based API used by the Desk...56.3 Corva Data APIThe Corva Data API serves the records stored in Corva datasets — one-second operational data, engineering c...55.8 Custom Connectors APICustom connectors allow you to create wrappers around REST or SOAP APIs for use in Power Apps, Power Automa...55.8 MuleSoft Anypoint Design Center APIThe Anypoint Design Center API provides access to the MuleSoft web-based API design environment for creatin...54.8

Developing 18 Usable, with meaningful gaps to close

Arazzo EngineOpen-source Python engine that executes Arazzo workflow specifications alongside OpenAPI operation definiti...53.9 Zilla MCP GatewayThe Zilla MCP Gateway is the AI-facing face of the Zilla engine. It terminates Model Context Protocol Strea...53.2 NetScaler Next-Gen APINetScaler Next-Gen API is a modern declarative RESTful API built on the OpenAPI 3.0 specification that allo...52.4 VMware Cloud Director OpenAPIModern RESTful API for VMware Cloud Director defined using OpenAPI standards providing cloud service delive...52.3 iGaming Tools MCP ServerFree public hosted MCP server (Streamable HTTP, no API key, read-only, not metered) exposing the same iGami...52.2 APIContext Open APIOpenAPI validation51.1 Spec Scoring APIPublic, no-auth REST API for scoring OpenAPI documents. GET /api/review/checks returns the full set of chec...50.5 Dream Sports Open APIThe Open API API from Dream Sports — 1 operation(s) for open api.49.7 Liblab MCP GeneratorGenerates a complete Model Context Protocol (MCP) server from an OpenAPI, Swagger, or Postman spec so AI ch...47.6 Liblab SDK GeneratorCloud-based generator that produces customizable, type-safe SDKs in seven target stacks (TypeScript, Python...47.6 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 Twenty Open APIOpenAPI schema discovery46.4 KiotaKiota generates strongly-typed, lightweight API clients from OpenAPI descriptions in C#, Dart, Go, Java, PH...46.3 3GPP Forge APIThe 3GPP Forge (forge.3gpp.org) is a self-managed GitLab instance where 3GPP publishes the machine-readable...45.8 Kareo Clinical Open APIThe Kareo Clinical Open API provides REST-based access to EHR clinical data, exposing patient clinical reco...44.8 Trieve REST APIProduction REST API for Trieve Cloud. Organizes resources around organizations, datasets, chunks, chunk gro...44.0 Hey API Openapi-Ts@hey-api/openapi-ts is an OpenAPI to TypeScript code generator that emits production-grade SDKs, types, val...42.8 Ignition Gateway REST APIThe Ignition Gateway REST API (available in Ignition 8.3+) provides an OpenAPI- compliant HTTP interface to...41.9

Thin 31 Limited public surface area

OgenThe ogen code generator. Invoked as a build-time CLI against a local OpenAPI v3 document — `ogen [options] ...38.1 Restate Open APIThe Open API API from Restate — 1 operation(s) for open api.37.9 OWASP ZAP Open APIThe Open API API from OWASP ZAP — 2 operation(s) for open api.37.6 Casey's General Stores Open APIThe Open API API from Casey's General Stores — 2 operation(s) for open api.37.5 Xano Generated User APIsThe REST APIs that Xano users build visually. Each API group is served at its own /api:{token} path on the ...37.3 AutoRest CoreThe AutoRest Core package (@autorest/core) is the central engine that orchestrates code generation from Ope...36.0 Mosaic Open APIThe Mosaic Open API exposes the workforce, project, and financial data Mosaic manages so firms can build cu...35.5 RefitterRefitter is a .NET source generator and CLI tool that produces Refit HTTP client interfaces from OpenAPI 2....35.5 Ambassador Blackbird API Development PlatformBlackbird is an API development platform that helps developers design, build, test, and manage APIs with AI...35.4 Ambassador Edge Stack Developer PortalThe Ambassador Edge Stack Developer Portal automatically detects and publishes API documentation, serving a...35.4 NASA Earthdata Open APIThe Open API API from NASA Earthdata — 1 operation(s) for open api.34.6 Kubescape In-Cluster Component API (Open Source)The open-source Kubescape Operator's in-cluster components (storage, kubevuln, gateway, operator, node-agen...34.3 Oapi-CodegenCommand-line tool and Go library that converts OpenAPI 3.0 and 3.1 specifications into Go server-side, clie...32.8 Apicurio CodegenApicurio Codegen generates Java JAX-RS server stubs and client code from OpenAPI specifications, enabling d...32.3 Apicurio Data ModelsApicurio Data Models is a Java and TypeScript library for parsing, validating, and manipulating OpenAPI and...32.3 Apicurio RegistryApicurio Registry is a high-performance, runtime registry for schemas and API designs. It stores and manage...32.3 Apicurio StudioApicurio Studio is a visual, zero-code API design tool for creating and editing OpenAPI and AsyncAPI specif...32.3 Vert.x OpenAPIVert.x OpenAPI provides OpenAPI 3.1 specification support for Vert.x, enabling contract-driven API developm...32.0 SchemathesisSchemathesis is a property-based API testing tool that automatically generates test cases from OpenAPI and ...31.7 Open Charge Map Open APIThe Open API API from Open Charge Map — 1 operation(s) for open api.31.6 UNIverse Research Information System APIThe REST backend of UNIverse (universe.unibas.ch), the University of Basel's research information system, a...31.4 Filecoin HTTP REST APIOpenAPI-specified HTTP REST interface for Filecoin nodes, covering chain resources (tipsets, blocks, execut...31.3 TypeSpec OpenAPI EmitterThe TypeSpec OpenAPI emitter converts TypeSpec definitions to OpenAPI 3.0 specifications. It supports HTTP ...31.1 LayerZero Open APIThe Open API API from LayerZero — 1 operation(s) for open api.31.0 Sourcegraph REST APIVersioned external REST API introduced in Sourcegraph 7.0 and intended as the stable integration surface go...30.2 what3words API Docs and OpenAPI RepositoryPublic repository hosting the OpenAPI specification, LLM files, and reference material for the what3words P...29.7 Hanyang University Open API Developer CenterHanyang University's own Open API platform, built and run by the university rather than bought from a vendo...29.3 Lumen OpenAPI Services (Level 3 legacy)The Level 3 / Lumen OpenAPI Services portal provided OpenAPI-described REST services such as the Lumen Loca...29.3 42Crunch API Security AuditThe 42Crunch API Security Audit performs automated static analysis of API definitions (OpenAPI 2, 3.0, 3.1 ...27.5 Morgan Stanley API Platform (REST)The institutional REST APIs on the Morgan Stanley API Platform let onboarded clients and third-party partne...27.5 ReDocReDoc is an open-source API documentation renderer for OpenAPI specifications, originally created by Rebill...26.8

Emerging 29 Early or largely undocumented

NSwagNSwag is an open source .NET toolchain for generating C# and TypeScript API clients and Swagger/OpenAPI spe...25.9 Chainguard Unified API SpecThe unified Chainguard API specification combines API v1 and v2 definitions in a single reference, useful f...24.3 Quarkus Open APIThe Open API API from Quarkus — 2 operation(s) for open api.24.2 VacuumVacuum is the world's fastest OpenAPI linter written in Go. It processes API specifications at lightning sp...22.5 NEXON Open APIProgrammatic access to per-game data (character, ranking, match, and metadata) for Nexon titles. Authentica...22.3 Coupang Open APIThe Coupang Open API is a RESTful seller (vendor) API for managing the full marketplace lifecycle including...22.1 SpectralSpectral is a flexible JSON/YAML linter and style guide enforcer with built-in support for OpenAPI (v3.1, v...22.0 Helidon Open APIThe Open API API from Helidon — 1 operation(s) for open api.21.2 Optic CLIThe Optic CLI provides OpenAPI diffing, linting and breaking-change detection from the command line, compar...21.0 ISO 20022 API Resources CatalogueThe ISO 20022 API Resources Catalogue, governed by the API Standards Evaluation Group (APISEG), provides re...20.7 DreddDredd is a language-agnostic command-line tool for validating an API description document against a backend...19.2 Flotiq APIAuto-generated RESTful and GraphQL APIs derived from user-defined content type definitions, enabling full C...19.2 OpenAPI VersioningOpenAPI handles versioning through the info.version field (using SemVer), the deprecated flag on individual...18.9 FastAPI FrameworkModern, fast web framework for building APIs with Python based on standard Python type hints.18.2 FastMCP OpenAPI and FastAPI IntegrationFastMCP can generate an MCP server directly from an existing OpenAPI 3.x description or a FastAPI applicati...18.2 OpenAPI SpecificationThe OpenAPI Specification (OAS) defines a standard, language-agnostic interface to RESTful APIs which allow...17.8 OpenAPI SpecificationThe OpenAPI Specification (OAS) defines a standard, programming language-agnostic interface description for...17.0 LoopBackLoopBack is a highly extensible Node.js and TypeScript framework for building APIs and microservices with b...16.4 DapperDoxDapperDox is an open-source API documentation generator that renders beautiful, customizable reference docs...16.2 SpecLynxStop wrestling with OpenAPI specs. SpecLynx OpenAPI Toolkit delivers the most effective way to author and m...15.2 SpecLynx ApiDOMA unified semantic parsing engine that underpins all SpecLynx products. ApiDOM parses OpenAPI, AsyncAPI, Ar...15.2 SpecLynx CLIA command-line interface for overlay operations, dereferencing, bundling, format conversion (JSON/YAML), an...15.2 SpecLynx EditorA browser-based OpenAPI editor with real-time validation, smart autocompletion, and live preview. No instal...15.2 SpecLynx Language ServiceAn LSP-compatible npm library (@speclynx/apidom-ls) providing 13 intelligent editing capabilities for API d...15.2 SpecLynx OpenAPI ToolkitA VS Code extension providing semantic editing, real-time validation, linting, and live preview for OpenAPI...15.2 Connexion Python FrameworkConnexion is a contract-first Python web framework that loads an OpenAPI specification and routes requests ...14.6 PortmanPortman is an open source CLI tool that auto-generates Postman collections with contract and variation test...12.4 JD Cloud OpenAPIJD Cloud OpenAPI is the programmatic control plane for JD Technology's public cloud — compute (VM), storage...12.2 API Insights AnalysisAPI Insights analyzes OpenAPI specifications (OAS v3, JSON or YAML) and produces detailed scorecards across...11.3

Minimal 3 Almost no public developer surface

OasdiffOasdiff is an open-source tool for detecting breaking changes and generating changelogs from OpenAPI specif...10.0 FastAPIModern, fast web framework for building APIs with Python 3.7+.9.8 X-Road (Straumurinn) API CatalogueIceland's X-Road data-exchange layer (Straumurinn). Government-to-government REST services that publish Ope...7.4

Companies reaching this through an API (52)

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 Agorapulse Aklivity Ambassador APIContext Bloomberg CData CenturyLink (Lumen Technologies) Chainguard Cisco Intersight Citrix NetScaler Clerk Corva AI Dream Sports FastMCP Filecoin Flotiq 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 Python Standard Library and Popular Quarkus REST Restate Snyk Sourcegraph Treblle Trieve Twenty University of Basel Versioning Protocols Vert.x VMware what3words Windmill

Show all 52 companies ↓

Xano Zuplo

Score breakdown

Frequency

67.1

log-scaled weighted occurrences

Breadth

3.8

spread across providers

Quality lift

52.8

mean composite of providers using it

Cohesion

10.5

strength of nearest seed neighbor

Where this tag comes from

Provider tag147

Api tag136

Openapi tag19

Openapi op tag29

Cohort brief

Auto-generated

The 143 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

143

of 147 on the roster

Mean Kin Score

44.1

+21.2 vs catalog 22.9

Mean Agent Readiness

29.6

+17.7 vs catalog 11.9

Spread

7.4–90.1

median 44.7 · σ 17.9

How the 143 split by band

Exemplar 14Strong 32Developing 39Thin 33Emerging 23Minimal 2

Facet averages, against the whole catalog

Facet	This cohort	Catalog	Difference	Scored
Developer Ergonomics	48	23.2	+24.8	143
Contract Quality	41	17.6	+23.4	143
Operational Transparency	35.6	13.7	+21.9	143
Access Clarity	44.3	26.5	+17.8	143
Contract Governance	16.9	6.3	+10.6	143
Discoverability	67.5	58.1	+9.4	143

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)	41%	14%	+27
MCP server (first-party)	40%	12%	+28
Agent Skills	0%	0%	0
OAuth scopes	21%	11%	+10
Security	97%	98%	-1
Arazzo workflows	6%	2%	+4
Governance rules	31%	14%	+17

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 90.1
2 Redocly 82.6
3 OpenMercantil 80.6
4 Postman 79.6
5 Zoho CRM 78.1
6 Cvent Event Cloud 71.9
7 Stoplight 71.8
8 Scalar 71.7
9 0xArchive 71.6
10 Archbee 70.9

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"

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OpenAPI

Providers using this tag (145)

APIs with this tag (124)