Best Unified API for Read and Write ATS Integrations (2025)
November 1, 2025
Recruiting software lives and dies by integrations. Job data, candidate profiles, and application statuses move across dozens of ATS platforms, and keeping them in sync is often slow, brittle, and maintenance-heavy.
A unified API simplifies this by normalizing every ATS's data model into one consistent schema—so you can connect once and access dozens of platforms like Greenhouse, Lever, Workable, and iCIMS. But not all unified APIs deliver real-time, read/write access that modern recruiting software needs.
This guide breaks down what to look for and why Unified.to leads in powering real-time, bi-directional ATS integrations.
What Is an ATS Unified API?
An ATS unified API is a single integration layer that connects your app to multiple Applicant Tracking Systems through one normalized schema.
Instead of managing each vendor's unique authentication, pagination, and webhook setup, you build once and access normalized Candidates, Jobs, Applications, Interviews, and Scorecards—with optional raw passthrough for vendor-specific fields.
For example:
- Read: Pull jobs, candidates, or interviews from any ATS
- Write: Create or update applications, candidates, or notes across systems
- Sync: Receive webhook events for real-time updates to hiring stages or feedback
What to Look For in a Unified API for ATS Integrations
When evaluating unified APIs for recruiting software, focus on technical depth and real-world usability—not just the integration count.
| Key Factor | Why It Matters |
|---|---|
| Full Read/Write Support | Many providers offer only read access. For real workflows—like pushing candidates or updating stages—you need bi-directional coverage. |
| Normalized Schemas | Consistent objects (Candidate, Job, Application) reduce engineering work and simplify testing. |
| Custom Fields and Objects | Recruiting data often includes unique schemas; API should support read/write for custom fields via metadata. |
| Real-Time Delivery | Native and virtual webhooks ensure events arrive instantly, even when the ATS lacks built-in support. |
| Zero-Storage Architecture | Avoid platforms that sync and store your users' data. A passthrough model minimizes compliance risk. |
| Security & Compliance | SOC 2 Type II, GDPR/CCPA compliance, PIPEDA/HIPAA compliance, optional credential storage in your own AWS Secrets Manager. |
| Developer Experience | SDKs, sandbox data, embedded auth components, and logging/observability. |
| AI-Readiness | Support for Model Context Protocol (MCP) to allow ATS data to LLMs as secure, callable tools. |
Why Unified.to Leads the ATS Category
Unified.to offers 63+ ATS integrations—including Greenhouse, Lever, Workable, SmartRecruiters, iCIMS, Bullhorn, Teamtailor, and JazzHR—through a single API.
Each integration supports read and write operations across candidates, jobs, applications, interviews, documents, and scorecards.
What sets Unified apart:
- Real-time, pass-through architecture — Every request fetches data live from the source API. No caching, no stale data.
- Virtual webhooks — When an ATS doesn't support native events, Unified detects and streams changes automatically.
- Zero-storage by design — No customer data ever stored or cached; traffic is stateless and regionalized (US/EU/AU).
- Custom fields & metadata API — Read/write access to custom objects (e.g., Salesforce custom fields) for flexible use cases.
- Developer-first UX — 7+ SDKs, embedded authorization components, sandbox data, and observability built in.
- Predictable, usage-based pricing — Scale from startup to mid-enterprise with transparent call-based pricing (Grow plan: 750K calls/month for $750+).
- AI-native integrations via Unified MCP — Allow real-time, permissioned ATS tools directly to LLMs (e.g., create candidate, update stage, log interview).
Example ATS Objects and Methods
Unified's ATS model covers every critical object, normalized across platforms:
| Object | Key Methods |
|---|---|
| Candidate | Create, List, Retrieve, Update, Remove |
| Job | Create, List, Retrieve, Update, Remove |
| Application | Create, List, Retrieve, Update, Remove |
| Interview | Create, List, Retrieve, Update, Remove |
| Document | Create, Retrieve, Update, Remove |
| Scorecard | Create, Retrieve, Update, Remove |
| Company | Create, Retrieve, Update, Remove |
This unified schema ensures consistent behavior across every ATS—even with custom fields or attachments.
Use Cases
- Source Candidates: Enrich, create, and sync candidates/applications across multiple ATSs.
- Assess Candidates: Trigger assessments and write results back as notes or scorecards.
- Promote Jobs: Post to job boards via supported ATS endpoints and track statuses.
- Track Applications: Subscribe to real-time stage changes or interview events.
- AI Agents: Let an LLM schedule interviews or update candidate status using Unified MCP tools.
Final Thoughts
If you're building recruiting or HR software that needs real-time, read/write ATS integrations, Unified.to is the best unified API available. It's fast to implement, secure by design, and ready for both SaaS and AI use cases.
With Unified.to, you can:
- Launch 60+ ATS integrations in days
- Power live hiring data for analytics, automation, or AI copilots
- Scale securely, without storing customer data
Start your 30-day free trial or book a demo to see it in action.