StackOne

What is StackOne?

StackOne is an integration infrastructure platform built specifically for AI agents, connecting them to over 200 SaaS systems through a single unified gateway. It gives AI agents access to 10,000+ pre-built actions across categories including HRIS, ATS, LMS, CRM, IAM, and document management, so developers don't need to build or maintain individual integrations for each provider. The platform handles authentication, rate limiting, retries, and data normalization under the hood, meaning agents interact with a single API regardless of which underlying system they're working with. It's aimed at developers and companies building AI agents that need to take real actions inside enterprise software like Workday, Salesforce, Greenhouse, or SharePoint.

Key Features

• Falcon Engine: StackOne's execution engine that handles authentication, rate limiting, retries, error handling, schema normalization, and caching to optimize context, token usage, latency, and reliability for AI agent actions.
• Connector Builder: Lets developers build production-ready custom connectors for REST, GraphQL, SOAP, OData, or proprietary APIs in minutes, without relying solely on pre-built options.
• Unified Documents API: Provides real-time read and write access to documents from SharePoint, OneDrive, Google Drive, Notion, and Confluence, including search, metadata extraction, and an embeddable file picker UI that honors source access controls.
• A2A Protocol Support: Implements the Agent2Agent protocol for standardized communication between agents, supporting text, audio, images, and files. Pre-built A2A agents per integration are available and dynamically customized based on account configurations.
• MCP and SDK Support: Offers managed MCP (Model Context Protocol) servers, an open-source ToolSet SDK in TypeScript and Python, and multi-language SDKs for custom logic and tool interfaces across AI frameworks.
• StackOne Defender: A payload scanning and classification layer for prompt injection protection, described as an open-source prompt injection guard for agents.
• Security and Compliance: Covers SOC2 Type II, HIPAA, and GDPR certification, with multi-tenancy, RBAC, audit logs, encrypted credentials, no default data storage, and regional data processing options.
• Organization and Project Management: Teams organize under Organizations with separate Projects that isolate API keys, linked accounts, integrations, and regional data residency settings for US or EU.

Use Cases

• Developers building AI agents for HR automation: Teams connect agents to HRIS and ATS platforms like Workday, SAP, BambooHR, and Greenhouse to automate workflows such as employee onboarding and benefits enrollment, reducing manual steps in hire-to-wire processes.
• Recruiting platforms needing multi-ATS coverage: Companies like Vizzy and Spotted Zebra have used StackOne to connect to multiple applicant tracking systems (including SAP, Workday, Greenhouse, Teamtailor, and Oracle) from a single integration layer, accelerating time-to-market for enterprise recruiting features.
• Sales and CRM automation: Agents connected through StackOne can pull deal data, score pipeline risk, and log call summaries back to CRM systems automatically, reducing the manual work of keeping records current after calls or meetings.
• Marketing and reporting automation: Marketing teams can connect agents to analytics, email, and campaign platforms to generate performance reports without manual data extraction from each tool.
• Security and compliance platforms: Drata, a security and compliance automation company, used StackOne for over 100 rapid integration deployments, connecting agents to IAM and document systems.

Strengths and Weaknesses

Strengths:

• Responsive customer support is the most consistently praised aspect across G2 reviews, with users noting the team's availability for integrations, troubleshooting, and updates.
• The unified API approach simplifies connecting to multiple enterprise systems, with documentation that users describe as thorough enough to support fast implementation.
• Pre-built connectors across a wide range of categories (HR, recruiting, CRM, documents, IAM) reduce the upfront effort needed to ship multi-integration features.
• G2 badges include High Performer, Easiest To Do Business With, and Users Love Us, based on 42 verified reviews with an overall rating of 4.6 out of 5.

Weaknesses:

• Some users report missing features such as filtering options and clearer field mapping documentation, which can lead to extra maintenance work.
• Sandbox testing coverage is limited for certain integrations, and some users have encountered bugs and SDK delays.
• Provider schemas sometimes include fields that don't exist in the actual API, which can cause agent failures even when the schema contract appears to be followed correctly.
• Rate limit errors from certain providers are embedded in response bodies rather than signaled through standard HTTP status codes, requiring additional monitoring and retry logic on the developer's side.

Pricing

• Starter: $0/month, includes 200+ pre-built connectors, 10,000+ pre-built actions, 1 custom connector via Connector Builder, 2 projects, managed auth and multi-tenancy, MCP protocol, AI action SDK, API access, in-app chat support, up to 1,000 free action calls per month, and $0.003 per additional call. No credit card required.
• Core: Contact StackOne for pricing. Includes everything in Starter plus premium pre-built connectors, unlimited custom connectors, 10 projects, A2A protocol, multi-region data processing, a dedicated Slack channel, SOC2 Type II certification, and $0.30 per 1,000 action calls (with volume discounts available).
• Enterprise: Contact StackOne for pricing. Includes everything in Core plus professional services, unlimited projects, any AWS region for data processing, custom SLAs and uptime guarantees, and $0.30 per 1,000 action calls (with volume discounts available).

FAQ

What does StackOne do?

StackOne connects AI agents to over 200 SaaS systems through a single API gateway, giving agents access to 10,000+ pre-built actions across HR, recruiting, CRM, documents, and other enterprise software categories. It handles authentication, retries, and data normalization so developers don't manage those concerns per provider.

Who is StackOne built for?

StackOne is built for developers and companies that are building AI agents and need those agents to take actions inside enterprise software systems. Customers in the dossier include recruiting platforms, HR automation tools, compliance platforms, and global mobility services.

Is StackOne free to use?

Yes, StackOne has a free Starter plan that requires no credit card. It includes 200+ connectors, 10,000+ actions, and up to 1,000 free action calls per month. Additional calls beyond that are billed at $0.003 each.

How much does StackOne cost?

The Starter plan is free. Core and Enterprise plans require contacting StackOne's sales team directly, as pricing is not publicly listed. Action calls on Core and Enterprise are priced at $0.30 per 1,000, with volume discounts available.

What integrations does StackOne support?

StackOne supports 200+ pre-built connectors including systems like Workday, Salesforce, Greenhouse, SAP, BambooHR, SharePoint, OneDrive, Google Drive, Slack, and Lattice, organized across categories such as HRIS, ATS, LMS, CRM, IAM, and document management.

Does StackOne support the MCP protocol?

Yes. StackOne offers managed MCP (Model Context Protocol) servers, available starting on the free Starter plan. MCP is a protocol used for defining tool interfaces for AI agents.

What is the Falcon Engine?

Falcon is StackOne's execution engine that manages the technical complexity of connecting agents to external APIs. It handles authentication, rate limiting, retries, caching, schema normalization, and low-latency data transformations so agents can execute actions reliably.

Does StackOne store data from connected systems?

By default, StackOne does not store data. It proxies requests in real-time, passing data between agents and providers without persisting it. Data residency options (US or EU, and any AWS region on Enterprise) are available for organizations with specific requirements.

What security certifications does StackOne hold?

StackOne holds SOC2 Type II, HIPAA, and GDPR certifications. Additional security features include RBAC, audit logs, encrypted credentials, multi-tenancy, and StackOne Defender for prompt injection protection.

What is StackOne Defender?

StackOne Defender is an open-source prompt injection guard. It scans and classifies agent payloads to help protect against prompt injection attacks, which are a known risk for AI agents interacting with external data sources.

Can I build custom connectors with StackOne?

Yes. The Connector Builder lets developers create custom connectors for REST, GraphQL, SOAP, OData, or proprietary APIs. The Starter plan includes one custom connector; the Core plan provides unlimited custom connectors.

What are the main complaints about StackOne?

Users on G2 report gaps in filtering options and field mapping clarity, limited sandbox coverage for some integrations, and occasional bugs or SDK delays. At a technical level, some providers return misleading error responses or have schema inaccuracies that can cause agent failures.

How does StackOne compare to Merge?

Both platforms offer unified API layers for connecting to enterprise SaaS systems. Based on available research, Merge is noted for an edge in enterprise scalability. StackOne is rated 4.6 out of 5 on G2 and is recognized for ease of integration and customer support quality.

What is the A2A protocol and does StackOne support it?

A2A (Agent2Agent) is a protocol for standardized communication between AI agents, supporting text, audio, images, and files. StackOne supports A2A on its Core and Enterprise plans, with pre-built A2A agents per integration that are dynamically configured based on account settings.

Where can I find StackOne's open-source code?

StackOne's AI Node SDK is available on GitHub under the Apache-2.0 license at github.com/StackOneHQ/stackone-ai-node. It is written in TypeScript and had 8 contributors as of early 2026.