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 12 Complete, well-documented, and agent-ready

SOAP APILegacy SOAP-based API for Marketing Cloud operations, including email sends, subscriber management, and dat...83.5 Salesforce Aura ComponentsSalesforce Aura Components is the legacy JavaScript component framework for building dynamic web applicatio...83.3 MailerLite Classic API (Legacy)The MailerLite Classic API serves legacy MailerLite Classic accounts. New integrations should target the cu...77.2 Vessel CRM API (v1, legacy)The first-generation Vessel CRM API, published under /crm/* with the vessel-api-token header and an accessT...72.1 Vessel Engagement API (v1, legacy)The first-generation Vessel Sales Engagement API, published under /engagement/* on api.vessel.land. Covers ...72.1 Thomas Jefferson University Hospital FHIR DSTU2 APIThe legacy Thomas Jefferson University Hospital DSTU2 FHIR endpoint listed in Epic's public R4 endpoint reg...71.1 Kraken Spot WebSocket API v1 (Legacy)Legacy Kraken Spot WebSocket API. Continues to operate alongside v2 but v2 is the recommended path for new ...70.6 Plaid Bank Transfer APIPlaid's Bank Transfer is part of the Plaid open-finance platform, exposing 13 documented endpoint(s) under ...68.2 Plaid Deposit Switch APIPlaid's Deposit Switch is part of the Plaid open-finance platform, exposing 4 documented endpoint(s) under ...68.2 Adobe Analytics 1.4 APIThe Adobe Analytics 1.4 APIs provide programmatic access to reporting, classifications, data sources, and r...67.4 ActiveCampaign v2 Legacy APIThe surviving v2 surface from ActiveCampaign — 1 operation, GET /api/2/template/share, which creates a shar...67.2 Enrich Labs Legacy API (v1/v2)The prior major version of the Enrich API, still live at api.enrich.so and still serving its own Swagger UI...66.9

Strong 23 Solid coverage with minor gaps

EGYM MMS API v1The legacy member-management-system API (Gym API v1). Publishes and reads member profiles, gym and user pro...66.0 Dolby.io Communications APILegacy Communications APIs for high-quality WebRTC voice and video conferencing with spatial audio, music m...65.5 Kensho Scribe Batch API v1Legacy v1 batch transcription endpoint (POST /api/v1/transcription). Superseded by the v2 batch API which d...64.6 Raygun Pulse RUM API (Legacy)Legacy enterprise-only Real User Monitoring read API at api.raygun.com/api/v1/pulse. Uses a Client ID/Secre...63.1 GitHub Legacy APIThe Legacy API from GitHub — 15 operation(s) for legacy.62.4 PortOne REST API (V1, legacy Iamport)Legacy V1 (Iamport) REST API on api.iamport.kr — token-authenticated (POST /users/getToken with imp_key/imp...61.4 TrustRadius Legacy Visitor Insights APIIdentified-company reporting, tagged `Legacy` by TrustRadius in its own specification. GET /reports/visitor...61.1 Nutshell Legacy JSON-RPC APINutshell's original JSON-RPC API, available since 2010. Nutshell states it is no longer adding new endpoint...60.8 Northern Powergrid Open Data Explore API v2.0The previous major version of the Opendatasoft Explore REST API, still served and still publishing its own ...60.7 Northern Powergrid Open Data Search API v1The original Opendatasoft Search API, still live on the portal and still carrying its own interactive conso...60.7 Oracle Health Millennium FHIR DSTU2 APIThe Cerner Millennium DSTU2 FHIR API supports legacy SMART on FHIR applications and integrations with Meani...60.7 Clearbit Risk APIScores an email address for fraud and abuse risk. Endpoint /v1/calculate?email=. Verified live 2026-08-13 (...60.6 Trestle RETSTrestle's RETS endpoint implements the RETS 1.8 specification on top of the same data catalog as the RESO W...60.0 IonQ Quantum Cloud API (v0.3 Legacy)The previous-generation IonQ Quantum Cloud REST API (v0.3) for submitting and managing jobs, characterizati...59.4 Temple Health FHIR DSTU2 APIThe legacy Temple Health DSTU2 FHIR endpoint listed in Epic's public DSTU2 endpoint registry under the orga...59.3 Jira Cloud Platform REST API v2Version 2 of the Jira Cloud platform REST API, offering the same operations as v3 but without Atlassian Doc...58.5 LeafLink Marketplace V2 APIThe legacy LeafLink Marketplace V2 REST API, currently at release 2.39.0. 66 paths and 111 operations for b...58.5 Exchange Web Services (EWS)Legacy SOAP-based API for Exchange Server providing comprehensive access to mailbox data and operations. Pl...57.2 Hydro-Québec Open Data Search API v1The legacy Opendatasoft Search API v1 still served on the Hydro-Québec open data portal. Verified live and ...56.8 Adobe Photoshop ExtendScript Scripting APIThe legacy scripting system based on ExtendScript, Adobe's implementation of ECMAScript 3. ExtendScript scr...55.8 Bluecore Transactional API (legacy)The original Bluecore Transactional API on https://api.bluecore.com/email/ - send a transactional or real-t...54.9 Atlassian Legacy APIThe Legacy API from Atlassian — 1 operation(s) for legacy.54.7 Claude Text Completions APILegacy API for generating text completions - deprecated in favor of the Messages API.54.4

Developing 26 Usable, with meaningful gaps to close

Airtel Smart API (legacy)Airtel's original partner developer programme, launched in 2017 and now an unmaintained legacy portal (the ...53.9 Arcadia Utility Cloud API (Legacy)The legacy Utility Cloud REST API — predecessor to the Plug API — still documented for existing integration...53.5 Azure AD Authentication Library (ADAL)Authentication library for Azure AD (being replaced by MSAL).52.8 Azure AD Graph API (Deprecated)Legacy API for accessing Azure AD (deprecated in favor of Microsoft Graph).52.8 Viator Affiliate API v1The legacy v1 affiliate-partner specification, a non-transactional subset covering utility services, destin...50.8 Viator Merchant API v1The legacy v1 merchant-partner specification still published by Viator, exposing taxonomy, product, photo, ...50.8 Decisiv Platform APIThe original XML Platform API for service providers and dealer systems, covering the lifecycle of a service...50.7 Dell WSMan APIWeb Services Management API for Dell server hardware management. WSMan provides a SOAP-based interface for ...50.5 Itron IEE Web ServicesLegacy web-service surface for Itron Enterprise Edition (IEE) Meter Data Management. Documented as a mix of...50.4 BrightEdge legacy APIOperation ported over from legacy API50.3 Maxar Content Catalog APILegacy Maxar Content Catalog API — the canonical search index against the WorldView / GeoEye / IKONOS / Qui...50.2 Adobe CEP (Common Extensibility Platform)The Common Extensibility Platform (CEP) is Adobe's legacy framework for building integrated HTML5 panels ac...49.7 MX Atrium APIThe legacy MX financial data connectivity API supporting over 48,000 data connections to thousands of finan...48.9 Apache Airflow Experimental API (Deprecated)The experimental API that preceded the stable REST API. This is deprecated and should not be used for new i...48.7 Udesk Open API v1 (legacy)Legacy Open API kept for existing integrations (tickets, customers, IM, call center, help center) with MD5 ...48.6 Opendatasoft Explore API v1 (Deprecated)Legacy REST API (v1) for searching datasets and records on Opendatasoft portals. Supports dataset search, d...47.1 Cvent SOAP API (Legacy)The Cvent SOAP API is the original legacy API for pushing and pulling data between Cvent and internal syste...45.4 PubChem PUG SOAP APILegacy SOAP/XML web service interface for PubChem providing structure search, identity search, and chemical...44.7 SP Energy Networks Open Data Search API (v1.0)The legacy Opendatasoft Search API v1.0 still served alongside Explore v2.1 on the SP Energy Networks Open ...44.5 MagicBell REST API v1The legacy MagicBell REST API (v1) for notification delivery, user management, and channel configuration. S...43.3 LSEG DataScope Select - SOAP APISOAP-based web service API for DataScope Select, providing extraction functionality for global pricing, ref...42.9 Trestle RETSTrestle's legacy Real Estate Transaction Standard interface, documented as compliant with RETS 1.8. RESO no...42.5 LiveIntent Privacy Management APISubmit data subject requests to LiveIntent programmatically to satisfy CCPA and GDPR obligations. Supports ...42.4 ReqRes Legacy APIThe Legacy API from ReqRes — 4 operation(s) for legacy.42.4 Elexon Legacy APIThe Legacy API from Elexon — 2 operation(s) for legacy.41.8 Cisco Expressway XML APILegacy XML-based API for configuration and status retrieval on Cisco Expressway systems. Uses HTTP Basic Au...41.3

Thin 25 Limited public surface area

IBM API Connect V1 APIThe IBM API Connect V1 API is the earlier generation management REST API for the API Connect platform, prov...39.1 Spredfast Conversations API (v1)The original Spredfast Conversations API, still live alongside v2 on api.spredfast.com — 27 operations for ...39.1 Webex XML APIThe Webex XML API is the legacy SOAP-style interface for deep integration with Webex Meetings. It supports ...37.4 ReadMe API (v1, Legacy)The legacy ReadMe API (HTTP Basic auth with an API key) for docs, categories, versions, custom pages, chang...37.2 Sezzle API v1The legacy Sezzle v1 API for merchants. Supports checkout creation and order completion via redirect-based ...37.1 Lever Candidates APILegacy Candidates endpoints maintained for backward compatibility. New integrations should use Opportunitie...36.7 Trip Ninja v2 Legacy APITwo further GitHub-published OpenAPI 3.0.0 documents describing the 2.0.0-era surface — a core document (/g...35.9 BrightEdge Technologies legacy APIOperation ported over from legacy API35.8 Open Commerce API (OCAPI)Legacy REST API for B2C Commerce Cloud, organized into Shop API, Data API, and Meta API. Authentication use...35.4 cPanel API 2 (Legacy)cPanel API 2 is the legacy XML/JSON API for cPanel-user operations. It remains supported for backward compa...34.9 Photon Bolt (Legacy, Deprecated)Legacy UDP-based Unity netcode product from Exit Games. No longer actively developed and not recommended fo...34.9 Photon PUN (Photon Unity Networking) APIPhoton Unity Networking 2, the original high-level Unity multiplayer SDK layered over the Photon Realtime t...34.9 Social Tables Events API (Legacy)The legacy Social Tables Events API provided REST access to events, venues, floor plans, diagrams, and seat...34.6 Commodity Futures Trading Commission Legacy APILegacy COT report format33.9 Snyk V1 API (Legacy)The original Snyk REST API. Still in use for project import, monitor, test, and certain reporting endpoints...33.8 Azure AD Graph API (Deprecated)Legacy REST API for Azure Active Directory (being replaced by Microsoft Graph).33.2 ClinicalTrials.gov Classic APIThe Classic API is the legacy ClinicalTrials.gov interface that preceded the Data API v2 and exposes full-s...33.1 Cloudbeds REST API v1.2 (Legacy)Earlier supported version of the Cloudbeds REST API. New integrations should target v1.3.32.5 Bitquery GraphQL API (V1)Legacy GraphQL endpoint covering Bitquery's V1 schema - kept for backward compatibility while customers mig...32.1 Nmbrs SOAP CompanyService (Legacy)Legacy SOAP v3 CompanyService (120+ operations, e.g. Company_GetCurrentPeriod, Run_GetList, RunRequest_Inse...30.3 Nmbrs SOAP DebtorService (Legacy)Legacy SOAP v3 DebtorService for the accountant/debtor tier that owns companies (e.g. AccountantContact_Get...30.3 Nmbrs SOAP EmployeeService (Legacy)Legacy SOAP v3 EmployeeService (300+ operations, e.g. Employee_GetCurrent, Contract_GetAll, Salary_GetCurre...30.3 Kanban Tool REST API v1Legacy REST API for Kanban Tool. Supports both XML and JSON formats, uses a resource-oriented endpoint stru...29.5 USGS Water Services (Legacy)The original USGS NWIS water services API providing streamflow, groundwater, water quality, and site inform...28.0 Sourcegraph GraphQL APIThe historical GraphQL API used by most Sourcegraph integrations to date. It is still available but Sourceg...27.1

Emerging 27 Early or largely undocumented

Entity Framework 6The mature and stable ORM for .NET Framework with Code First, Database First, and Model First workflows.25.0 SmartSimple Web Services (SOAP) APIThe legacy SOAP Web Services API, exposed per instance via a WSDL at /WS/services/UtaUpdate?wsdl (for examp...25.0 Cloudability API v1 (Legacy)The legacy v1 API remains available for older integrations covering cost reporting and dimensions. Apptio r...24.3 Zylo Legacy API (Cleanshelf-era)Legacy v1.0 endpoints retained from the original Cleanshelf product line. New integrations should use the m...23.8 Zonos Checkout REST API (legacy)Legacy REST integration surface for Zonos Checkout, listed on the Zonos REST API reference index. No base U...23.7 Zonos Classify REST API (legacy)Legacy REST endpoints for harmonizing a catalog to HS codes one item at a time or in bulk, with a group ide...23.7 Zonos Landed Cost REST API (legacy)Legacy REST endpoint that returns a complete breakdown of the duties, taxes and fees making up a total land...23.7 Zonos Order Complete REST API (legacy)Legacy REST endpoint that accepts the details of a shopper's completed order and returns the Zonos-specific...23.7 Zonos Rating REST API (legacy)Legacy REST endpoint returning international shipping rates for carriers and service levels. Documented pat...23.7 OlympusDAO Legacy APIDeprecated WunderGraph-compatible /operations routes.23.5 Sage Intacct XML APILegacy XML API providing programmatic access to general ledger, accounts payable, accounts receivable, orde...23.3 Sage Intacct XML APILegacy XML-based API for Sage Intacct accounting and financial management, providing broad coverage of ever...22.0 Blackboard Learn SOAP API (Legacy)Legacy SOAP web services for Blackboard Learn integrations.21.8 Chainguard API v1Chainguard API v1 is the legacy REST API for the Chainguard platform, covering the same broad surface as v2...21.8 Fleet Complete Legacy Integration WebAPIOlder, regionally hosted OAuth REST surface predating the Unity GraphQL API, still referenced in Fleet Comp...21.8 Habiteo Site JSON API (WordPress JSON API plugin)A second, older JSON surface on www.habiteo.com, served by the WordPress "JSON API" plugin at /api/. GET ht...21.1 Glassdoor Partner API (Legacy)Historical REST API that exposed job listings, employer reviews, salary reports, and company metadata to ap...17.3 Ally Invest API (Legacy / Retired)The legacy Ally Invest brokerage REST API, inherited from Ally's 2016 acquisition of TradeKing. It offered ...16.9 Khan Academy API v1 (Legacy / Internal)Legacy REST API previously documented at api-explorer.khanacademy.org (now redirects). Some endpoints under...16.9 AngularJS Core APIThe AngularJS (Angular.js, version 1.x) core framework API for building dynamic single-page web application...15.9 Aporia Guardrails (Legacy)The original Aporia Guardrails product offered millisecond-latency policy enforcement on LLM prompts and re...15.7 Aporia ML Observability (Legacy)Aporia ML Observability provided monitoring for classical ML models including drift detection, data quality...15.7 AI Firewall (Legacy)The Robust Intelligence AI Firewall provided runtime guardrails for LLM and ML applications, screening prom...15.6 Algorithmic AI Red Teaming (Legacy)Algorithmic AI Red Teaming was Robust Intelligence's automated adversarial testing product for ML and LLM m...15.6 API BlueprintAPI Blueprint is a Markdown-based specification language for describing web APIs, originally created by Api...15.4 RAML (RESTful API Modeling Language)RAML is a YAML-based modelling language for RESTful APIs, originally created by Mulesoft. RAML 1.0 (2016) i...15.4 WSDL / SOAPThe Web Services Description Language (WSDL) is the historical XML-based interface definition language for ...15.4

Minimal 2 Almost no public developer surface

Coca-Cola Enterprises Location API (Legacy)Historical Coca-Cola Enterprises (CCE) Location API that exposed Coca-Cola product availability and bottler...10.1 Coca-Cola Enterprises Product API (Legacy)Historical Coca-Cola Enterprises (CCE) Product API that exposed product catalog metadata and was published ...10.1

Score breakdown

Frequency

51.0

log-scaled weighted occurrences

Breadth

0.8

spread across providers

Quality lift

83.2

mean composite of providers using it

Cohesion

36.6

strength of nearest seed neighbor

Where this tag comes from

Api tag117

Provider tag17

Openapi tag8

Openapi op tag64

Cohort brief

Auto-generated

The 117 providers in the APIs.io catalog tagged Legacy, scored on the Kin Score. Every figure below is computed from the catalog — nothing here is written.

Providers

117

all scored

Mean Kin Score

39.1

+18.4 vs catalog 20.7

Mean Agent Readiness

+13.3 vs catalog 9.7

Spread

0–83.5

median 41.3 · σ 21.1

How the 117 split by band

Exemplar 10Strong 24Developing 25Thin 22Emerging 19Minimal 17

Facet averages, against the whole catalog

Facet	This cohort	Catalog	Difference	Scored
Contract Quality	40.7	17.5	+23.2	117
Developer Ergonomics	35.7	17.9	+17.8	117
Operational Transparency	28.3	11.3	+17	117
Access Clarity	38.9	22.3	+16.6	117
Contract Governance	20.4	6.4	+14	117
Discoverability	69.8	60.4	+9.4	117

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)	32%	16%	+16
MCP server (first-party)	13%	7%	+6
Agent Skills	0%	0%	0
OAuth scopes	25%	9%	+16
Security	91%	88%	+3
Arazzo workflows	16%	2%	+14
Governance rules	44%	13%	+31

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 Salesforce Marketing Cloud 83.5
2 Salesforce 83.3
3 MailerLite 77.2
4 Vessel 72.1
5 Jefferson Health 71.1
6 Kraken 70.6
7 Plaid 68.2
8 Adobe Analytics 67.4
9 ActiveCampaign 67.2
10 Enrich 66.9

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/legacy"

All tags

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

As a scored cohort

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

The distribution (Pro)

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

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Legacy

Providers using this tag (117)

APIs with this tag (115)