ATS Unified APIs: What to Look For, Use Cases, and Options

September 29, 2025

Hiring workflows live across dozens of tools—ATS platforms, assessment systems, sourcing extensions, calendars, and job boards. Building one-off ATS integrations for each vendor is slow and brittle. Auth flows, webhooks, pagination, rate limits, and object shapes all differ, and your team ends up maintaining the same plumbing repeatedly.

An ATS Unified API fixes that. Instead of writing one integration per provider, you connect once to a normalized API that abstracts key differences. Candidates, applications, jobs, interviews, and activities are available through a single surface—ready for analytics, workflows, and AI copilots.

What is an ATS Unified API?

An ATS unified API is a translation layer between your app and multiple applicant tracking systems—e.g., Greenhouse, Lever, Workable, iCIMS, Ashby, Bullhorn, SmartRecruiters, and many more. With one schema and one auth flow, you can read and write standard objects and still access raw payloads when you need provider-specific fields.

• Direct integration: bespoke builds per vendor—unique auth, pagination, rate limits, and webhooks to implement and maintain.
• Unified approach: normalizes Candidate, Application, Job, Interview, and Activity/Note while preserving raw passthrough for edge cases.

Result: faster launches, less integration debt, and consistent access patterns across platforms. And if you're powering AI features, a real-time unified API plus MCP (Model Context Protocol) lets your agent fetch and act on ATS data securely—no glue code.

What to Look For in an ATS Unified API

When you evaluate providers, look under the hood—not just at a logo grid.

• Coverage depth — Leading ATS vendors (Greenhouse, Lever, Workable, SmartRecruiters, iCIMS, Bullhorn, Teamtailor, JazzHR, Jobvite, etc.) plus adjacent HR/CRM systems your workflows touch.
• Normalized schemas — Clean, consistent objects for Candidate, Application, Job, Interview, and Activity/Note; support for attachments/documents and scorecards; normalized relationships.
• Custom fields & raw passthrough — Read/write for custom fields and custom objects via a metadata API; escape hatches for vendor-specific endpoints.
• Real-time delivery — Native webhooks when the ATS supports them; virtual webhooks (provider-managed polling, change detection, retries) when it doesn't—so your app always receives events consistently.
• Zero-storage architecture — No caching of customer data; passthrough requests fetch live data directly from the source to avoid stale results and reduce compliance scope.
• Security & compliance — SOC 2 Type II, GDPR/CCPA, optional storage of credentials in your own cloud KMS/AWS Secrets Manager, IP allow-listing, and externalized logs.
• Developer experience — SDKs in major languages, embedded auth components, sandbox data, logging/observability, and a true "build once per category" model.
• Pricing model — Usage-based pricing that scales predictably (not per connection or per customer), with transparent overage rates.
• AI-readiness — Built-in MCP so ATS data and actions are callable as LLM tools with permissioned, real-time execution—no prompt hacks or custom bridges.

Use Cases for ATS Unified APIs

1. Source Candidates – Enrich and stage sourced prospects; create candidates/applications in the ATS and sync updates back. (e.g., Greenhouse, Lever, Workable)
2. Assess Candidates – Trigger assessments, store results as notes/scorecards, update application stages programmatically.
3. Promote Jobs – Post to multiple job boards via supported ATS endpoints; keep postings/statuses in sync where supported by the ATS or via adjacent job board connectors.
4. Track Applications – Subscribe to stage changes and interview events; maintain real-time pipelines, SLAs, and SLA breach notifications.
5. Agentic workflows – Use MCP to let a copilot schedule interviews, add notes, or move stages—securely and auditable—without custom glue.

ATS Unified API Options in the Market

Not all "unified APIs" behave the same. Some are sync-first (great for BI), others are real-time (better for agents and live product flows). Use this chart to evaluate coverage, schema fidelity, webhook model, storage, and pricing—then map each to your workload.

Why Unified.to Leads in the ATS Category

Most unified API platforms started with payroll or CRM. Recruiting has more edge cases: custom stages, job board variance, assessment add-ons, attachment handling, and noisy webhooks.

We built our stack specifically for real-time, zero-storage delivery that's AI-ready out of the box.

• Broad ATS coverage + adjacent systems — Over 60 ATS connectors (Greenhouse, Lever, Workable, SmartRecruiters, iCIMS, Bullhorn, Teamtailor, JazzHR, Jobvite, and more) with unified models, plus HR, CRM, file storage, calendars, and messaging to support end-to-end workflows.
• Real-time model — Native webhooks when available and Virtual Webhooks when not—so your product consumes a single, reliable event interface without writing polling code.
• Security by design (no data stored) — We never cache or store your customers' ATS data; every call fetches from the source. SOC 2 Type II, GDPR/CCPA, credential storage in your AWS Secrets Manager, log streaming to your Datadog, and IP allow-listing.
• AI-native with MCP — Expose real-time, permissioned ATS tools to LLMs (Claude, GPT, Gemini) so your copilot can take action—update stages, leave notes, schedule interviews—safely and deterministically.
• Developer-friendly — 7+ SDKs, embedded auth/SSO components, sandbox & observability, and a consistent schema across categories—so you can launch multiple integrations in days, not quarters.
• Transparent, usage-based pricing — Start free for 30 days; predictable unit economics as you scale (no per-connection lock-in).

Integrating with ATSs shouldn't block your roadmap—or your AI strategy. With Unified.to, you integrate once and unlock ATS coverage that's real-time, secure, and AI-ready.

If your roadmap includes sourcing, assessments, analytics, or agentic recruiting features, start your free 30-day trial or book a demo.