What Unified API Solutions Support a Large Number of Integrations?

Unified.to supports the most integrations of the nine unified API platforms compared here: 1639 integrations across 36 categories, as of October 2026. Truto is the nearest on count, listing 800+ integrations as of 8 October 2026. StackOne lists 540+ connectors (543 live as of 8 October 2026), and Merge, Apideck and Paragon each list between about 120 and 250 by their own counts, while Finch, Kombo and Nylas stay within one vertical: HR and payroll, HR and recruiting, or email and calendar. For SaaS and AI product teams, the count is the first filter; what each integration can read, write and send as change events decides what you can build.

This breakdown compares the nine platforms on breadth (how many integrations and categories) and depth (objects, fields, writes, events and auth), using each vendor's public documentation. Competitor figures carry the date they were checked.

• Merge.dev lists 233 integrations across eight categories as of 2 October 2026, most of them HRIS and ATS.
• Apideck claims 200+ integrations; as of 8 October 2026 its per-category pages sum to 175.
• Paragon is an embedded integration platform with 124 integrations across 13 docs categories (8 October 2026).
• Truto lists 800+ integrations (840 connectors in its llms.txt) under 50+ catalogue categories, with 29 normalized unified APIs, as of 8 October 2026. Of the 840, 338 have no unified API and are reached through its proxy or MCP tools, and 297 are in beta. Reads are pass-through by default.
• Kombo lists 250+ integrations by its own count as of 8 October 2026, across HRIS, ATS, LMS and assessment.
• StackOne lists 540+ connectors and 33,000+ provider-native actions for AI agents (543 live as of 8 October 2026); its HRIS, ATS, CRM, LMS and accounting unified APIs are now "Legacy". Finch and Nylas round out the list with category-focused offerings.

Breadth: Who Has the Most Integrations?

Depth: What Can You Actually Do With These Integrations?

Depth varies more between these platforms than integration counts do: they differ most on custom-field access, which features sit behind higher plans, which writes each connector supports, and how quickly changes reach your app. Each multi-category platform below is described on the same five dimensions:

• Objects: which records (e.g. messages, deals, files) are normalized per integration
• Fields: how custom fields and raw provider data are reached
• Read/Write: whether you can create and update records, or only fetch them
• Webhooks: how change events reach you, and how often
• Auth: how OAuth, API keys and token refresh are handled

Unified.to

• Objects: Normalized objects per category across 36 categories
• Fields: Normalized schemas plus passthrough; the Metadata API looks up custom fields on 50 platforms in the docs (as of October 2026), and writes go through the normalized model
• Read/Write: Reads and writes through the normalized model, routed to the source at request time
• Webhooks: Native webhooks where the source sends them; virtual webhooks that detect changes and deliver events at a 1-minute minimum interval on paid plans (60 minutes on the 30-day free trial)
• Auth: Embedded authorization components for React, Angular, Vue, Svelte and plain JavaScript; your own OAuth app supported; token management and permission scopes

Merge.dev

• Objects: Common Models per category; custom objects on Professional and Enterprise
• Fields: Remote Data, Remote Fields, Field Mapping and Passthrough, all on Professional and Enterprise
• Read/Write: Reads and writes; writes go to the source at request time, with /meta field discovery and async and bulk writes
• Webhooks: Merge webhooks on every plan; daily sync on Launch; source webhooks and faster syncs on Professional and Enterprise
• Auth: Managed OAuth, scopes, and refresh

Apideck

• Objects: Standardized per API category (CRM, HRIS, etc.)
• Fields: Custom fields returned in custom_fields; saved per-customer mapping on Scale and above
• Read/Write: Operations published per connector and resource; support varies
• Webhooks: Native webhooks, plus virtual webhooks typically every 24 hours, adjustable by plan (plan intervals not published)
• Auth: OAuth and API keys; Apideck stores and refreshes the tokens

Paragon

• Objects: Action-based in ActionKit; Managed Sync normalizes File Storage, CRM and Ticketing
• Fields: Per provider in ActionKit; normalized plus customFields in Managed Sync
• Read/Write: Yes, through provider-specific actions
• Webhooks: Native webhooks where the provider supports them, otherwise polling once a minute
• Auth: Drop-in OAuth components

Truto

• Objects: Fully configurable; supports custom schemas
• Fields: All vendor fields available via real-time passthrough
• Read/Write: Reads and writes where each integration's API allows; methods are published per integration (as of 8 October 2026, 7 of 28 ATS integrations support a write)
• Webhooks: Unified webhooks on about a dozen integrations; elsewhere, opt-in RapidBridge sync jobs on a cron schedule (5-minute minimum, as of 8 October 2026)
• Auth: API key and basic authentication, plus OAuth 2.0 through Truto's OAuth app by default or your own client ID and secret; where an integration supports more than one method, the end customer picks in the Connect UI (as of 8 October 2026)

StackOne

• Objects: Provider-native actions per connector; normalized "Unified Actions" only for documents, identity and permissions; its HRIS, ATS, CRM, LMS and accounting unified APIs are Legacy, "no longer in active development" (as of 8 October 2026)
• Fields: The provider's own fields by default; proxy only on the Legacy APIs ("Proxy Request (Legacy)"); no custom-field lookup documented for current actions
• Read/Write: Create, update and delete actions published per connector; depth varies by connector
• Webhooks: Native webhooks; webhooks for systems without native ones in early access; polling events only on the Legacy APIs (1 hour default, down to 5 minutes where the provider supports time-based filtering)
• Auth: Managed authentication with token refresh; StackOne's shared OAuth apps for testing or your own for production; BYOK for stored credentials

Finch / Kombo / Nylas

These three go deep within one vertical rather than across categories:

• Finch: pay statements typed by earning, tax and deduction; writes limited to deductions and contributions on Pro and Premier, on 26 providers in its provider data (as of 8 October 2026)
• Kombo: HRIS, ATS, assessment and LMS; 3-hour default sync, with source webhooks on 22 integrations arriving in 10 to 20 seconds (as of 8 October 2026)
• Nylas: full read and write on email, calendar and contacts, with mailbox-native objects (threads, drafts, folders, signatures), but no category outside communications (as of 8 October 2026)

Real-Time Sync: Which Unified APIs Deliver Changes Fastest?

Among the multi-category platforms compared here, Unified.to and Paragon detect changes fastest when a source sends no native webhooks: as of October 2026, Unified.to's virtual webhooks run at a 1-minute minimum interval on paid plans (60 minutes on the trial), and Paragon polls once a minute. Kombo syncs every 3 hours by default, Apideck typically every 24 hours, and Merge daily on its Launch plan, with faster syncs on Merge's Professional and Enterprise plans. Event speed matters most for AI agents, dashboards and user-facing sync, where a stale read is visible to your customer.

Final Takeaway

If you're building an integration layer into your product, choose based on your required categories, object depth, and sync latency.

• Choose Unified.to if you want:
  • Largest integration surface
  • Reads and writes through one normalized model
  • Native and virtual webhooks (1-minute minimum interval on paid plans)
  • Passthrough access and LLM-ready data for agents/copilots
• Choose Merge if you're focused on HR or ATS and your reads tolerate your plan's sync cadence: daily on Launch, faster on Professional and Enterprise.
• Choose Apideck if you're focused on HR or CRM, accept EU hosting, and can live with change events about once a day.
• Choose Truto if you're prioritizing passthrough access or custom object support, and StackOne if your agents need each provider's own actions with prompt-injection scanning and per-user permission policies.
• Use Finch, Kombo, or Nylas only if your integrations stay within one vertical, such as payroll, HR and recruiting, or email.

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Written by Mallory Greene.

About the author: Mallory Greene is Head of Marketing at Unified.to. She writes about integration infrastructure, unified APIs, and MCP for technical teams. Based in Toronto.