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What is a Unified API?

A unified API provides a single, standardized interface to interact with multiple third-party providers. Instead of learning each provider’s unique API format, authentication scheme, and data model, you write code once, and StackOne handles the differences. What StackOne normalizes:
  • Data models – Consistent field names and structures across providers (e.g., files in Google Drive, SharePoint, and Dropbox all return the same schema; users in Google Workspace, Okta, and 1Password all return the same schema)
  • Authentication – OAuth, API keys, and tokens are managed per-provider; you just pass an x-account-id header
  • Pagination – Cursor-based pagination works the same regardless of whether the provider uses offsets, pages, or cursors
  • Error formats – Standardized error responses with provider-specific details when available
Building AI agents? Use the MCP Server, an AI Toolset SDK, or the Actions API (RPC) instead — same data, optimized for LLM tool calling.

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Benefits of the ATS API

StackOne’s APIs interfaces with the underlying systems in real-time, allowing for immediate updates and synchronization across platforms.
With a focus on security, StackOne’s architecture avoids unnecessary data storage, maintaining compliance with data protection regulations.
The platform provides both synthetic and native webhooks, enabling real-time notifications for candidate and job posting changes.
StackOne offers pre-built connectors with a wide range of ATS platforms, simplifying the integration process.

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Key Features

The table below shows key features of the ATS API that make recruitment easier, from real-time application tracking and offer Management:

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StackOne SDKs & OpenAPI Specification

Use our official SDKs for faster integration. Build with language-native libraries. Full list here.

OpenAPI Specification

Popular SDKs

Node.js Java (JVM) PHP Ruby

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Entity Model and Relationships

The following diagram illustrates the key entities within the ATS API: The following table outlines key entities within the ATS system and provides a brief description of each:

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Use cases

Job Board Application Tracking

Job boards can post positions, accept applications, and monitor candidate progress through normalized recruitment stages via a single API that handles the complete application lifecycle.

Interview Insights

Interview intelligence platforms can access structured interview data, update scorecards, and analyze candidate performance across standardized evaluation criteria.

Candidate Screening

Screening solutions can retrieve applications, process candidate data through qualification algorithms, and update application stages with acceptance or rejection reasoning using standardized fields.

Assessment & Background Checks

Providers can receive candidate evaluation orders, update test results, and automatically update application statuses with standardized scoring data that feeds directly into the hiring decision process.