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 6 Complete, well-documented, and agent-ready

Optimizely Specifications APIThe Specifications API from Optimizely — 7 operation(s) for specifications.81.3 Arazzo Specification (Redocly Tooling)Arazzo is the OpenAPI Initiative's specification for describing multi-step API workflows; Redocly is a prim...81.1 CarsXE International VIN Decoder APIVIN decoding for non-US vehicles, returning make, model, year, and market-specific trim/spec data for inter...72.4 CarsXE Specifications APIVIN decoding for North American and international vehicles — 2 operations (getVehicleSpecs, getInternationa...72.4 CarsXE Vehicle Specifications APIVIN decoding and comprehensive vehicle specification lookup. Returns year, make, model, trim, engine, drive...72.4 Clerk OpenAPI SpecificationsPublic repository of OpenAPI specifications for Clerk's APIs, used as the source for generated SDKs and doc...70.5

Strong 6 Solid coverage with minor gaps

Aeris Specifications APISpecification Management APIs are for user to get specifications info61.9 Autodesk ACC AutoSpecs APIThe ACC AutoSpecs API retrieves Smart Register data from specification PDFs and submittal requirements with...60.3 Procore Specifications APIThe Specifications API from Procore — 43 operation(s) for specifications.60.3 Fusio Specification APIThe specification API from Fusio — 3 operation(s) for specification.59.4 ParlayAPI Specification APIOpenAPI and AsyncAPI specs describing the REST and streaming surfaces.58.4 Accruent Specifications APIThe Specifications API from Accruent — 2 operation(s) for specifications.56.1

Developing 15 Usable, with meaningful gaps to close

Buildpack SpecificationThe Buildpack API (currently 0.12) defines the contract between an individual buildpack and the lifecycle. ...53.5 Image Extension SpecificationImage extensions emit Dockerfile snippets applied by the `extender` lifecycle binary to the build and/or ru...53.5 Platform SpecificationThe Platform API (currently 0.15) defines how platforms (pack, kpack, Tekton Pipelines, GitLab Auto DevOps,...53.5 Jentic API AI-Readiness Framework (JAIRF)Technical specification for evaluating how interpretable, operable, and trustworthy an API is for AI system...52.2 Cox Automotive Specifications APIThe Specifications API from Cox Automotive — 1 operation(s) for specifications.51.5 CDEvents SpecificationCDEvents is a common specification for Continuous Delivery events that enables interoperability across CI/C...50.6 Buildpack API SpecificationThe Buildpack API is the contract between a buildpack and the lifecycle. It defines the detect and build ex...47.7 Distribution API SpecificationThe Distribution API specifies how buildpacks and builders are packaged as OCI artifacts, signed, and distr...47.7 Platform API SpecificationThe Platform API is the contract between the CNB lifecycle and a platform such as pack, kpack, or a CI runn...47.7 VTEX Specification APIThe Specification API from VTEX — 2 operation(s) for specification.47.5 3GPP Forge APIThe 3GPP Forge (forge.3gpp.org) is a self-managed GitLab instance where 3GPP publishes the machine-readable...46.3 AsyncAPI SpecificationThe AsyncAPI Specification is an open standard for describing asynchronous and event-driven APIs. It provid...44.2 HAProxy Specification APIThe Specification API from HAProxy — 1 operation(s) for specification.42.7 API BlueprintAPI Blueprint is a high-level API design language created by Apiary for designing and documenting web APIs....42.6 Hey API Specifications APIThe Specifications API from Hey API — 1 operation(s) for specifications.41.5

Thin 20 Limited public surface area

Acelab Material Hub Platform APIThe private production API behind the Acelab Material Hub web application and Revit add-in. It is not a pub...38.3 Equipmentwatch Specifications APIThe Specifications API from Equipmentwatch — 2 operation(s) for specifications.36.5 CloudEvents SpecificationThe CloudEvents specification defines a set of metadata attributes that must be present in every event, inc...36.2 CloudEvents SQL (CESQL)CloudEvents SQL (CESQL) is a v1.0 specification that defines a standardized query language for filtering an...36.2 OCI Spec for Rustoci-spec-rs is a Rust implementation of the OCI Runtime, Image, and Distribution Specifications, providing ...35.5 Specright APIREST API over Specright's specification data. Forty-six operations across six areas: token issuance, specif...34.2 Traceable Specifications APIDownload OpenAPI, WSDL, and other API specification files generated from discovered traffic.33.3 Notary Project Signing SpecificationThe Notary Project specification defines the signature envelope format, trust store and trust policy for co...32.8 THORChain Specification APIThe Specification API from THORChain — 2 operation(s) for specification.31.8 Trustworthy Workload Identity (TWI) SpecificationsA working group and set of Internet Draft specifications under the Confidential Computing Consortium that d...30.0 Kalshi AsyncAPI SpecificationMachine-readable AsyncAPI description of the Kalshi WebSocket streaming API. Suitable for generating async ...29.4 Apache Arrow Format SpecificationThe Apache Arrow columnar format specification defines the binary layout for in-memory columnar data, inclu...29.3 API-Fiddle Specifications APIManage API specifications within projects.29.3 AsyncAPILinux Foundation-hosted specification for event-driven APIs. Describes servers, channels, operations, messa...29.3 CloudEventsCNCF-graduated specification (graduated January 25, 2024) for describing event data in a common way. Define...29.3 docomo Mail IMAP InterfaceThe docomo Mail IMAP interface is the one machine-interface specification NTT DOCOMO publishes openly, with...28.3 W3C APIThe W3C API provides programmatic access to W3C data including specifications, working groups, editors, tra...27.7 W3C Specifications APIThe Specifications API from W3C — 3 operation(s) for specifications.27.7 MCP SpecificationThe authoritative protocol definition for the Model Context Protocol, maintained at modelcontextprotocol.io...26.8 APIs.json SpecificationThe APIs.json specification defines a machine-readable JSON or YAML format for describing API operations. U...26.7

Emerging 28 Early or largely undocumented

in-toto Attestation FrameworkThe in-toto Attestation Framework provides a specification for generating verifiable claims about any aspec...25.8 in-toto Attestation SpecificationThe in-toto specification defines the metadata format for recording software supply chain steps. It include...25.8 VINaudit Specifications APIThe Specifications API from VINaudit — 1 operation(s) for specifications.25.4 NIST SP 800-207 Zero Trust ArchitectureThe foundational specification of the Zero Trust security model. Defines the seven tenets, the PDP/PEP/PA l...25.2 Smithy IDLThe Smithy Interface Definition Language (IDL) is a specification for defining API models using shapes and ...25.1 TUF Repository SpecificationThe TUF specification defines the structure of update repositories including the root, targets, snapshot, a...25.0 CNI SpecificationThe CNI specification defines the interface between container runtimes and network plugins. It specifies ho...24.0 BICS Specification APIThe specification API from BICS — 1 operation(s) for specification.22.2 RISC-V ISA SpecificationsThe canonical RISC-V Instruction Set Architecture specifications including the Unprivileged ISA (RV32I/RV64...21.5 Jakarta Bean Validation Specification 3.1The Jakarta Bean Validation 3.1 specification defines the constraint model, annotation processor, Validator...20.8 TLA+ Community ModulesA curated collection of TLA+ snippets, operators, and modules contributed by the TLA+ community, providing ...17.8 TLA+ Specification ExamplesA collection of TLA+ specifications of varying complexity covering distributed algorithms, consensus protoc...17.8 Apache Parquet Format SpecificationThe core specification for the Parquet columnar storage format.17.2 JSON:APIJSON:API is a specification for how a client should request that resources be fetched or modified, and how ...16.3 OpenAPI SpecificationThe OpenAPI Specification (OAS) defines a standard, language-agnostic interface to RESTful APIs which allow...16.3 FOCUS (FinOps Open Cost and Usage Specification)FOCUS defines a common normalized data schema for cloud and technology billing data. The specification is d...14.2 Overture SchemaCanonical open schema specification for all Overture themes, maintained in the OvertureMaps/schema GitHub r...13.6 Cap'n Proto Encoding (Wire Format)The Cap'n Proto encoding specification defines the binary wire format. The in-memory layout is the wire for...12.6 Cap'n Proto RPC ProtocolCap'n Proto's RPC protocol is a capability-based RPC layer that supports promise pipelining, object referen...12.6 Cap'n Proto Schema LanguageThe Cap'n Proto schema language is used to define message types in .capnp files that are then compiled into...12.6 Jakarta JSON BindingJakarta JSON Binding (formerly JSON-B) is a binding framework for converting Java objects to and from JSON ...11.9 Jakarta JSON ProcessingJakarta JSON Processing (formerly JSON-P) provides an API to parse, generate, transform, and query JSON doc...11.9 Jakarta RESTful Web ServicesJakarta RESTful Web Services (formerly JAX-RS) is the API specification for developing web services that fo...11.9 Jakarta ServletJakarta Servlet is a server-side Java API for handling HTTP requests and generating dynamic responses. It p...11.9 Jakarta ValidationJakarta Validation (formerly Bean Validation) provides an object-level constraint declaration and validatio...11.9 Jakarta WebSocketJakarta WebSocket defines a standard API for creating server and client endpoints that communicate using th...11.9 Margo SpecificationMargo defines an open standard specification for interoperability of edge applications, devices, and orches...11.2 WebAssembly Component Model SpecificationThe Component Model specification repository under the W3C WebAssembly Community Group. Contains design doc...11.2

Minimal 1 Almost no public developer surface

OpenAPI Initiative APIAPI for accessing OpenAPI Initiative resources, specifications, and tooling ecosystem documentation for def...8.6

Companies reaching this through an API (43)

These companies publish an API, specification or operation carrying “Specification” 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.

3GPP Accruent Aeris Apache Arrow Apache Parquet API-Fiddle Apiary Autodesk Bean Validation BICS CarsXE Cloud Native Buildpacks Confidential Computing Consortium Container Network Interface (CNI) Continuous Delivery Foundation Cox Automotive Equipmentwatch Events Fusio HAProxy In-Toto Jakarta EE Kalshi Margo Model Context Protocol (MCP) Notary Project NTT Docomo Optimizely Overture Maps Foundation ParlayAPI Redocly REST RISC-V International Smithy Specright The Update Framework (TUF) THORChain Traceable VINaudit VTEX W3C Youki Zero-Trust Security Model

Score breakdown

Frequency

55.7

log-scaled weighted occurrences

Breadth

0.7

spread across providers

Quality lift

27.0

mean composite of providers using it

Cohesion

10.4

strength of nearest seed neighbor

Where this tag comes from

Api tag76

Provider tag31

Openapi tag17

Openapi op tag43

Cohort brief

Auto-generated

The 30 providers in the APIs.io catalog tagged Specification, scored on the Kin Score. Every figure below is computed from the catalog — nothing here is written.

Providers

of 31 in the catalog

Mean Kin Score

26.5

+4.3 vs catalog 22.2

Mean Agent Readiness

15.4

+3.4 vs catalog 12

Spread

4.1–78

median 22.2 · σ 17.1

How the 30 split by band

Exemplar 1Strong 1Developing 5Thin 7Emerging 12Minimal 4

Facet averages, against the whole catalog

Facet	This cohort	Catalog	Difference	Scored
Contract Quality	27.8	17.2	+10.6	30
Developer Ergonomics	33.4	23.2	+10.2	30
Operational Transparency	21.1	13	+8.1	30
Contract Governance	12	6.5	+5.5	30
Discoverability	59.7	57.9	+1.8	30
Access Clarity	12.4	23.9	-11.5	30

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)	13%	13%	0
MCP server (first-party)	13%	12%	+1
Agent Skills	0%	0%	0
OAuth scopes	7%	11%	-4
Security	90%	98%	-8
Arazzo workflows	3%	2%	+1
Governance rules	43%	16%	+27

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 Postman 78
2 GSMA 54.3
3 Buildpacks Io 53.5
4 AGNTCY 49
5 AsyncAPI 44.2
6 Hey API 41.5
7 Open Education API 39.8
8 Acelab 38.3
9 CloudEvents 36.2
10 Craft.io 32.9

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/specification"

All tags

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

As a scored cohort

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

The distribution (Pro)

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

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.

Specification

Providers using this tag (30)

APIs with this tag (76)