established · 1.6 capabilitymarket resourcedomain

Calendar

Score 25.8 / 100 105 providers 83 APIs Search apis.io →
Variants seen in the corpus: Calendarcalendar

Providers using this tag (105)

Ranked by API Evangelist rating — Exemplar and Strong are expanded by default.

Exemplar 4 Complete, well-documented, and agent-ready
NylasCommunicationsContactsEmail14 APIs76.2AlphaAIFinancial NewsStock MarketSEC FilingsInsider Trading3 APIs73.7Clear StreetCompanyFinancial-ServicesCapital MarketsPrime Brokerage23 APIs67.4Microsoft OutlookContactsEmailEnterprise4 APIs66.5
Strong 10 Solid coverage with minor gaps
Chili PiperSchedulingLead RoutingMeetingsSales16 APIs65.5ThetaDataFinancialMarket DataOptionsStocks14 APIs65.2EODHDFinancialMarket DataStock OptionsStocks11 APIs64.9CycleCalcsAstronomySpaceScienceEphemeris30 APIs64.4VendastaCompanySoftware-as-a-ServiceMarketplaceSMB38 APIs63.3AlpacaFintechTradingStocksCrypto23 APIs62.7Unified.toIntegrationUnified-API140 APIs60.4Microsoft ExchangeCollaborationContactsEmail20 APIs57.2SIXFinancialMarket DataStocksReference Data9 APIs56.0Microsoft Office 365CloudCollaborationEnterpriseMicrosoft12 APIs54.8
Developing 29 Usable, with meaningful gaps to close
Amazon WorkMailBusiness CommunicationEmailExchange80 APIs53.2VaultREReal-EstateAustraliaNew ZealandPropTech3 APIs52.8CalendarificPublic APIsHolidaysWorldwide3 APIs52.7RittenCompanyBehavioral HealthEMREHR1 API52.2Holiday APIHolidaysPublic HolidaysObservances4 APIs51.8HostawayVacation RentalsShort-Term RentalsProperty ManagementChannel Manager16 APIs51.2Checkiday - National Holiday and Event APIHolidaysEventObservances1 API51.1ZoomChatCollaborationCommunicationsMeetings47 APIs51.1EOD Historical DataFintechMarket DataStocksETFs20 APIs50.7API Calendrier Marocain | Jours Fériés & Ouvrables REST + SDK PythonHolidaysMoroccoBusiness Days3 APIs50.5KolayIKCompanyHuman ResourcesHRPayroll11 APIs50.4MicrosoftFortune 10059 APIs47.8Google CalendarAvailabilityEventGoogle4 APIs47.7Google WorkspaceCollaborationEmailProductivity29 APIs47.5Microsoft OfficeCollaborationDocumentsMicrosoftOffice9 APIs47.0CharthopCompanyHRPeople AnalyticsHRIS87 APIs46.4Acuity SchedulingSchedulingAppointmentsBooking3 APIs46.0SavvyCalSchedulingAppointmentsAvailability6 APIs45.4CCP GamesCompanyGamingGamesMMO31 APIs45.0CrunchDAOCompanyCrypto Web3Machine-LearningData Science70 APIs44.3TreasurySpringCompanyFintechCash ManagementTreasury13 APIs44.3airbnb11 APIs44.1Wispr AICompanyVoiceSpeech-to-TextDictation50 APIs43.7KumospaceCompanyVirtual OfficeRemote WorkCollaboration23 APIs42.4EVE OnlineAuthenticationAuthorizationGamingImage50 APIs40.5XigniteFinancialMarket DataStocksReal-Time23 APIs40.4D2L BrightspaceLMSLearning Management SystemEdTechEducation13 APIs39.6Zoho MailEmailMailCollaborationMessaging4 APIs39.6University of WarsawEducationHigher EducationUniversityPoland7 APIs39.3
Thin 29 Limited public surface area
Reclaim.aiArtificial IntelligenceSchedulingProductivity83 APIs39.0ZohoAnalyticsCollaborationCRMCustomer Service34 APIs38.5HospitableVacation RentalShort-Term RentalProperty ManagementAirbnb8 APIs37.6CronofySchedulingAvailabilityBooking5 APIs37.5Planning CenterChurch ManagementChMSFaithGiving9 APIs37.5PetExecPet CareBoardingDaycareGrooming14 APIs37.3PurplebricksReal-EstateUnited KingdomProperty ListingsOnline Estate Agency13 APIs36.9UplistingVacation RentalShort-Term RentalChannel ManagerProperty Management9 APIs35.1Microsoft 365ProductivityCollaborationEmail9 APIs34.8TableCheckRestaurantReservationsBookingHospitality14 APIs34.3Microsoft Office SuiteCloudCollaborationDocumentsMicrosoft-36510 APIs33.9Bitrix24CRMCollaborationProject ManagementTask36 APIs33.4Microsoft Products APIsAzureCloudEnterpriseMicrosoft14 APIs33.1SpurwingSchedulingAppointmentsBooking4 APIs33.0Technical University of MunichUniversityHigher EducationEducationGermany6 APIs33.0Cal.comProductivitySchedulingOpen-Source22 APIs32.2Microsoft Office ProductsCloudEnterpriseMicrosoftOffice9 APIs31.4Google Workspace APIsCloud StorageCollaborationEmailOffice Suite4 APIs31.0Microsoft SuiteCloudEnterpriseProductivitySoftware-as-a-Service13 APIs30.8Microsoft Office Pack9 APIs30.4Moon-APIAstrologyAstronomyLunarMoon7 APIs30.2Office 365CloudCollaborationDocumentsEmail5 APIs30.1AmieCompanyConsumerProductivity29.9DoodleSchedulingMeetingsGroup Polls1 API29.6Acuity SchedulingAppointment SchedulingBookingScheduling5 APIs29.5ClockwiseArtificial IntelligenceSchedulingFocus Time1 API29.5VetspireVeterinaryPractice ManagementPIMSHealthcare12 APIs28.9ZcalSchedulingBookingMeetings3 APIs28.6Exchange Data InternationalFinancialMarket DataCorporate ActionsReference Data24 APIs27.0
Emerging 13 Early or largely undocumented
ZimbraEmailCollaborationMessaging1 API25.3DentrixDentalPractice ManagementHealthcareDentistry7 APIs20.2University of California, Santa BarbaraEducationHigher EducationUniversityStudent Information System7 APIs19.7Cisco Collaboration Hybrid SolutionsCallingCollaborationHybrid CloudMeetings12 APIs19.3SupafaxCompanyEmailAI Assistant19.2FountainHiringRecruitingOnboardingApplicant Tracking2 APIs18.9CronCompanyConsumerScheduling16.3Microsoft ApplicationsCloudCollaborationEnterpriseMicrosoft9 APIs16.2CabinetCompanySchedulingExecutive Assistant14.2TherapyNotesBehavioral HealthEHRPractice ManagementMental Health4 APIs14.1AWSTCompanyProductivitySchedulingDocument-Management13.3VelaCompanySchedulingArtificial IntelligenceAI Agents11.6LEAPLegalLegal TechPractice ManagementLegal Accounting5 APIs11.2
Minimal 20 Almost no public developer surface
SaturnCompanySchedulingConsumer10.4CEPS (Centre for European Policy Studies)BrusselsData GovernanceEU PolicyEuropean Union2 APIs7.4TownCompanyArtificial IntelligenceAgentsPersonal Assistant7.3Festivo Public HolidaysPublic APIs1 API6.2Church CalendarPublic APIs1 API5.7Czech Namedays CalendarPublic APIs1 API5.7Hebrew CalendarPublic APIs1 API5.7LectServePublic APIs1 API5.7Nager.DatePublic APIs1 API5.7Namedays CalendarPublic APIs1 API5.7Non-Working DaysPublic APIs1 API5.7Public HolidaysPublic APIs1 API5.7UK Bank HolidaysPublic APIs1 API5.7AcompliCompanyEmailMobileProductivity5.0Non-Working DaysPublic APIs1 API5.0Russian CalendarPublic APIs1 API5.0ScoopCompanyFuture Of WorkHybrid WorkWorkplace Scheduling5.0TimeBlocksCompanySchedulingProductivity5.0Woven SoftwareCompanySchedulingProductivity5.0ExamityProctoringExam IntegrityOnline AssessmentEdTech5 APIs4.0

APIs with this tag (82)

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 3 Complete, well-documented, and agent-ready
Nylas APIThe Nylas v3 REST API provides programmatic access to email, calendar, contacts, meeting notetaking, schedu...76.2AlphaAI REST APIREST API for relevance-scored, ticker-linked financial news. Fifteen read-only operations across news feeds...73.7Clear Street Calendar APIAccess clocks and financial calendars for market sessions and events.67.4
Strong 8 Solid coverage with minor gaps
ThetaData Calendar APIThe Calendar API from ThetaData — 3 operation(s) for calendar.65.2EODHD Economic Events Calendar APIProvides a global economic calendar of macroeconomic releases including country, event name, scheduled time...64.9CycleCalcs MCP ServerHosted stateless Streamable HTTP MCP server exposing 11 astronomy tools backed by the v2 REST endpoints. Re...64.4Vendasta Meetings APIMeetings (CalendarHero) API for creating meetings, adding contacts, messaging and searching. Scope-gated wi...63.3Alpaca Calendar APIThe Calendar API from Alpaca — 2 operation(s) for calendar.62.7Unified.to calendar APIThe calendar API from Unified.to — 11 operation(s) for calendar.60.4SIC Clearing Day Calendar APIScheduling information for the electronic payment services provided by SIX Interbank Clearing Ltd - clearin...56.0Microsoft Office 365 Calendar APIAccess and manage Outlook calendar events, calendars, and calendar groups. Supports scheduling, meeting man...54.8
Developing 21 Usable, with meaningful gaps to close
VaultRE APIThe core VaultRE REST API - the open API a third-party developer integrates an agency website or applicatio...52.8VaultRE Integrator APIA distinct set of endpoints that operate at the integrator level rather than at an individual agency-accoun...52.8Ritten External APIThe Ritten External API is the public REST contract for Ritten integrating partners. It covers patients (cr...52.2Hostaway Calendar APIRead and update the per-listing availability and nightly pricing calendar. Supports per-day retrieval, batc...51.2Zoom Calendar APIThe Zoom Calendar API enables developers to manage calendar events, automate scheduling, sync across platfo...51.1EOD Historical Data Calendar APICalendar events including earnings, IPOs, splits, dividends, and trends50.7KolayIK Calendar APIThe Calendar API from KolayIK — 5 operation(s) for calendar.50.4Microsoft Calendar APIAccess and manage Outlook calendar events47.8Google Calendar APICreate and manage calendars, events, and attendees.47.5Outlook Mail APIAPI for accessing and managing email, calendar, contacts, and tasks in Outlook.47.0Charthop calendar APIThe calendar API from Charthop — 10 operation(s) for calendar.46.4CCP Games Calendar APIThe Calendar API from CCP Games — 3 operation(s) for calendar.45.0CrunchDAO calendar APIThe calendar API from CrunchDAO — 2 operation(s) for calendar.44.3TreasurySpring Calendar APIGet Calendar information44.3airbnb Calendar APIOperations for managing listing availability, pricing, and calendar synchronization across platforms.44.1Wispr AI Calendar APIThe Calendar API from Wispr AI — 6 operation(s) for calendar.43.7Kumospace Calendar APIThe Calendar API from Kumospace — 7 operation(s) for calendar.42.4EVE Online Calendar APIThe Calendar API from EVE Online — 6 operation(s) for calendar.40.5Xignite Earnings Calendar APICompany earnings announcement dates and earnings calendar data from the earningscalendar.xignite.com service.40.4D2L Brightspace Calendar APICourse calendar events.39.6University of Warsaw calendar APIAcademic calendar events39.3
Thin 27 Limited public surface area
Zoho CalendarThe Zoho Calendar API provides REST endpoints to customize calendar features, allowing you to manage calend...38.5Hospitable Calendar APINightly availability, pricing, and restrictions per property.37.6Planning Center Calendar APIChurch calendaring, events, and facility resources.37.5PetExec Calendar APICompany-wide and per-owner reservation calendars by date range.37.3Purplebricks Outlook Sync APIAgent-facing microservice that reads and toggles Outlook calendar synchronisation for a local property expe...36.9Uplisting Calendar APIAvailability, prices, and restrictions per property and date.35.1Microsoft 365 Calendar APIThe Calendar API from Microsoft 365 — 1 operation(s) for calendar.34.8Microsoft Graph APIUnified REST API providing a single endpoint to access data and intelligence across Microsoft 365, Microsof...34.8TableCheck calendar APIThe calendar API from TableCheck — 1 operation(s) for calendar.34.3Outlook API (Office.js)JavaScript API for building add-ins and automating Microsoft Outlook.33.9Bitrix24 Calendar APIThe Calendar API from Bitrix24 — 21 operation(s) for calendar.33.4Bitrix24 REST APITenant-scoped REST API for managing CRM entities, deals, leads, tasks, calendars, telephony, disk files, us...33.4Microsoft Products APIs Calendar APIOutlook calendar events for the signed-in user.33.1Office 365 APIsAPIs for Office 365 applications including Outlook, Calendar, Contacts, and Files.33.1Outlook JavaScript APIAPI for building Outlook add-ins for email, calendar, and contacts.31.4Google Workspace APIs Calendar APIThe Calendar API from Google Workspace APIs — 3 operation(s) for calendar.31.0Microsoft Suite Calendar APIThe Calendar API from Microsoft Suite — 2 operation(s) for calendar.30.8Outlook Mail APIAccess to Outlook mail, calendar, contacts, and tasks via Microsoft Graph.30.8Outlook Mail APIAPI for accessing and managing email messages, calendars, and contacts.30.4Moon-API Calendar APIThe Calendar API from Moon-API — 1 operation(s) for calendar.30.2Microsoft Graph APIThe primary API for Office 365, providing access to data and intelligence in Microsoft 365, Windows 10, and...30.1Outlook Calendar APIAccess and manage calendar events, meeting requests, and calendar groups.30.1Acuity Scheduling REST API v1REST API for managing appointments, appointment types, clients, calendars, availability, intake forms, prod...29.5Clockwise REST APIREST API for the Clockwise AI calendar optimization platform, providing programmatic access to focus time m...29.5Vetspire Schedule & Appointments APIGraphQL operations over the Schedule domain - list appointments for a location and date range, read provide...28.9EDI Central Bank Calendar APICentral bank meeting and announcement calendar via the GetLatestCentralBankCalendar endpoint.27.0EDI Economic Calendar APIForward-looking economic calendar events via the GetLatestEconomicCalendar endpoint.27.0
Emerging 9 Early or largely undocumented
Dentrix Appointments & Scheduling APIRead the schedule and book, reschedule, or cancel appointments. In the Dentrix Developer Program this maps ...20.2UCSB Academics APIsAPIs covering the life-cycle of campus, departments, and students, including Academic Curriculums, Academic...19.7Webex Hybrid Services APIManage Webex Hybrid Calendar, Hybrid Call Service, Hybrid Message, Video Mesh nodes, and other connectors t...19.3Fountain Hire API v2REST API for the Fountain Hire product, covering applicants (create, retrieve, update, delete, list, latest...18.9Microsoft Graph APIUnified API endpoint for accessing Microsoft 365, Windows 10, and Enterprise Mobility + Security services.16.2Office 365 APIAPIs for Office 365 services including Outlook, OneDrive, and SharePoint.16.2Outlook Mail APIAccess and manage email, calendar, and contacts in Outlook.16.2TherapyNotes Scheduling API (Modeled)Modeled capability area for appointments, recurring schedules, and reminders. TherapyNotes offers native on...14.1LEAP Calendar APIModeled calendar/diary and appointment-scheduling surface, evidenced by production Marketplace scheduling i...11.2
Minimal 14 Almost no public developer surface
CEPS Events ListingsCEPS maintains a calendar of policy events, conferences, task force meetings, and webinars that can be embe...7.4Festivo Public HolidaysFastest and most advanced public holiday and observance service on the market6.2Church CalendarCatholic liturgical calendar5.7Czech Namedays CalendarLookup for a name and returns nameday date5.7Hebrew CalendarConvert between Gregorian and Hebrew, fetch Shabbat and Holiday times, etc5.7LectServeProtestant liturgical calendar5.7Nager.DatePublic holidays for more than 90 countries5.7Namedays CalendarProvides namedays for multiple countries5.7Non-Working DaysSimple REST API for checking working, non-working or short days for Russia, CIS, USA and other5.7Public HolidaysData on national, regional, and religious holidays via API5.7UK Bank HolidaysBank holidays in England and Wales, Scotland and Northern Ireland5.7Non-Working DaysDatabase of ICS files for non working days5.0Russian CalendarCheck if a date is a Russian holiday or not5.0Examity Appointments (Scheduling) APICreate, reschedule, and cancel proctoring appointments for a test-taker against a registered exam, and quer...4.0

Score breakdown

Frequency
61.4
log-scaled weighted occurrences
Breadth
2.9
spread across providers
Quality lift
40.3
mean composite of providers using it
Cohesion
11.3
strength of nearest seed neighbor

Related tags

Meetings 24 co-occurrences Mail 16 co-occurrences Scheduling 37 co-occurrences Productivity 32 co-occurrences Outlook 8 co-occurrences Email 25 co-occurrences Drives 8 co-occurrences OneDrive 7 co-occurrences

Where this tag comes from

Provider tag49
Api tag79
Openapi tag32
Openapi op tag113

Cohort brief

Auto-generated

The 105 providers in the APIs.io catalog tagged Calendar, scored on the Kin Score. Every figure below is computed from the catalog — nothing here is written.

Providers
105
all scored
Mean Kin Score
33.8
+13.1 vs catalog 20.7
Mean Agent Readiness
20.6
+10.9 vs catalog 9.7
Spread
4–76.2
median 34.3 · σ 19.2
How the 105 split by band
Exemplar 4Strong 10Developing 29Thin 29Emerging 13Minimal 20
Facet averages, against the whole catalog
FacetThis cohortCatalogDifferenceScored
Contract Quality 38 17.5 +20.5 105
Access Clarity 36.3 22.3 +14 105
Developer Ergonomics 29.3 17.9 +11.4 105
Operational Transparency 21.9 11.3 +10.6 105
Discoverability 68.2 60.4 +7.8 105
Contract Governance 9.2 6.4 +2.8 105

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
ArtifactThis cohortCatalogDifference
MCP server (any) 25% 16% +9
MCP server (first-party) 12% 7% +5
Agent Skills 0% 0% 0
OAuth scopes 30% 9% +21
Security 94% 88% +6
Arazzo workflows 9% 2% +7
Governance rules 23% 13% +10

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. 1 Nylas 76.2
  2. 2 AlphaAI 73.7
  3. 3 Clear Street 67.4
  4. 4 Microsoft Outlook 66.5
  5. 5 Chili Piper 65.5
  6. 6 ThetaData 65.2
  7. 7 EODHD 64.9
  8. 8 CycleCalcs 64.4
  9. 9 Vendasta 63.3
  10. 10 Alpaca 62.7
Top by Agent Readiness
  1. 1 AlphaAI 71
  2. 2 EODHD 66.3
  3. 3 Clear Street 63.2
  4. 4 Nylas 52.4
  5. 5 Alpaca 51.3
  6. 6 CycleCalcs 49.4
  7. 7 Chili Piper 47.1
  8. 8 Charthop 46.4
  9. 9 SIX 46.2
  10. 10 Microsoft Outlook 46
All 105 members of this roster resolve to a scored provider in the catalog.Generated from the catalog build of 25 August 2026, across 26891 providers, using the same computation served by the APIs.io cohort API. Briefs are published for rosters of 5 or more scored providers; below that a distribution is not meaningful.

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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

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curl "https://apis.io/api/v1/tags/calendar"
All tags 
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As a scored cohort 
curl "https://apis.io/api/v1/cohorts/tag/calendar"
The distribution (Pro) 
curl "https://apis.io/api/v1/cohorts/tag/calendar/stats" \
  -H "X-API-Key: $APIS_IO_KEY"

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