# Top unified API options in 2025 to replace custom SaaS connectors (and when to look beyond them) Building and maintaining custom SaaS connectors for your product is painful. Unified APIs promise a simpler path: connect once, get access to many apps. For product teams, this sounds like a good replacement for hand-coding integrations one by one. But unified APIs aren’t the only option, and in many cases, they may not be enough. While [Ampersand](https://www.withampersand.com/?utmsource=blog) does not provide a Unified API to connect to your customer's data, this post is intended to provide a neutral breakdown of the leading Unified API providers, while introducing an alternative path: integration infrastructure built for real-time, deep, enterprise-grade integrations. ## What is a Unified API? Unified APIs aggregate multiple SaaS applications into a single, normalized schema. Instead of building one-off integrations with Salesforce, HubSpot, or NetSuite, you integrate once with the unified API provider. ### General Benefits - Generally quick time to market where a single API can be deployed to connect to your customer's data - Single schema to code against to increase the breadth of your product offering - Coverage across dozens (sometimes hundreds) of apps that your customers may require ### General Limitations - Schema drift: Every customer’s CRM or ERP is configured differently - Shallow sync: Often limited to polling, with delayed data freshness - One-size-fits-all: Can’t handle per-tenant customization or advanced workflows - Operational load: Rate limits, retries, and auth handling often pushed back to you ## Top Unified API Providers ### Merge.dev **Pros** - Broad category coverage: Merge supports HRIS, ATS, ticketing, and more, making it appealing for teams that want to launch quickly without custom-building dozens of connectors. - Polished developer experience: Their documentation, testing sandboxes for higher paying tiers, and consistent onboarding process lowers the barrier for teams seeking breadth of integrations. - Rapidly expanding catalog: Merge is adding new connectors monthly, expanding its already broad integrations library. **Cons** - Hidden custom fields: Normalized schemas flatten or abstract away tenant-specific fields like Salesforce custom objects, limiting tailored enterprise experiences (docs). - Polling-based syncing: Data freshness depends on polling intervals, which can lag minutes or longer, limiting real-time workflows. - Operational overhead: Because customization is not architecturally baked in, a lot of teams use the Merge passthrough and end up handling custom rate limits, retries, and per-tenant schema drift, creating hidden engineering costs. ### Apideck **Pros** - Extensive API catalog: Covers HR, accounting, payments, file storage, and commerce, letting SaaS teams integrate across categories from a single platform. - Products by Solutions: Bucketed solutions by use cases help teams decide what integrations they need by giving users step-by-step guides to follow. - Transparent pricing: Clear pricing and a well-documented developer portal make Apideck attractive for SMB SaaS adoption. **Cons** - Tiered feature gating: Core capabilities such as higher data limits or certain connectors require upgrading to more expensive tiers, creating unpredictable costs for scaling teams. - Weak enterprise alignment: Apideck is best positioned for SMB-focused SaaS teams, and enterprises often find gaps in critical features like tenant isolation, compliance controls, or advanced security certifications. - Polling-driven architecture: Most integrations rely on polling intervals for data sync, which introduces latency and prevents use cases that demand immediate or real-time data availability. ### Unified **Pros** - Developer-focused tooling: Modern schemas and simple APIs emphasize productivity, appealing to SMBs and startups. - MCP offering: Pairing their unified API with an MCP server expanded their total product catalog to over 300 sources across more than a dozen categories. - Flexible pricing: Iterative pricing plans and rapid updates make it approachable for growth-stage companies. **Cons** - Limited coverage: Integration catalog is narrower than Merge or Apideck, sometimes requiring supplemental solutions. - Schema constraints: Normalized schemas restrict per-tenant customizations and deeper workflows (docs). - Ecosystem still maturing: As a younger company, its enterprise reliability and scaling practices are being proven. ### Finch **Pros** - HR/payroll specialization: Finch connects to ADP, Gusto, and Paychex with one unified API, simplifying fragmented HR and payroll integrations. - Normalized HR schema: Consistent data models make compliance-heavy use cases like benefits and onboarding easier to build. - Credibility in HR tech: Trusted in the HR ecosystem for tackling complex payroll integrations. **Cons** - Narrow domain: Coverage is limited to HR and payroll, requiring additional tools for CRM or accounting. - Polling limitations: Polling-based syncs limit real-time use cases like compliance reporting or instant dashboards. - Not general-purpose: Beyond HR and payroll, Finch does not add value, making it insufficient as a standalone solution (FAQs). ### Codat **Pros** - Financial systems coverage: Provides a unified API for accounting, banking, and commerce, connecting to QuickBooks, Xero, Sage, and Netsuite. - Rich data models: Offers detailed API docs for transactions, balance sheets, and financial statements, simplifying complex financial integrations. - Strong fintech partnerships: Well-established in the finance ecosystem with partnerships that validate its credibility. **Cons** - Vertical-only: Focused on finance and accounting with no CRM or HR coverage. - Schema tradeoffs: Normalized schemas can struggle with custom accounting configurations, leading to gaps. - Limited scope: Robust in finance, but SaaS teams with multi-category needs must combine it with other providers. ### When Unified APIs Aren’t Enough If your product needs: - Real-time, sub-second sync (not polling every 10 or 15 minutes) - Bi-directional workflows (not just data access) - Per-customer schema handling (no “lowest common denominator” schemas) - Enterprise-grade reliability (auth refreshes, rate-limit aware retries, tenant isolation) … a unified API may fall short. ## The Alternative: Integration Infrastructure with Ampersand Unified APIs solve the problem of getting something connected quickly, but they’re not built for the realities of enterprise SaaS or AI-era applications. Ampersand isn’t a unified API. **It’s integration infrastructure**: the foundation your product team uses to build and run deep, real-time, production-grade integrations without reinventing the plumbing. ### What makes Ampersand different from Unified APIs? - Real-time, event-driven integrations - Unified APIs typically rely on polling, which means customer data is stale by the time it arrives. Ampersand’s Subscribe Actions let you listen to events with sub-second latency, which power AI agents, workflows, and analytics that actually run in real-time. - Per-customer schema drift handling - No two Salesforce or NetSuite tenants are configured the same. Unified APIs flatten everything into a lowest-common-denominator schema, leaving you blind to the custom fields your customers rely on. Ampersand’s platform handles per-tenant drift automatically, so every customer sees the integration reflect their reality. - Enterprise reliability baked in - With Ampersand, you don’t have to build the (ugly but necessary) plumbing like: - Rate-limit aware retries - Isolated tenant deployments (so customers don’t share infra or quotas) - Automatic token refresh & auth flows - Sub-second webhooks that won’t drop events - Instead of duct-taping these yourself, you get them as part of the platform. - AI-ready SDK and MCP server - As more teams ship AI-native products, integrations become the limiting factor. Ampersand’s SDK and MCP server let you expose data and actions from Salesforce, HubSpot, NetSuite, and more directly into your AI agents — without custom coding a new connector each time. - Control and flexibility - Unlike a unified API, you’re not locked into one schema. You own the integration logic, map fields per tenant, and define workflows that match your product’s and customer's needs. Ampersand just gives you the infrastructure to do it quickly and reliably. ## Creating a Unified Data Model with Ampersand Ampersand’s declarative framework makes it possible to define a unified data model without locking customers into the rigid, one-size-fits-all schemas that typical unified APIs enforce. With Ampersand, you get the benefits of a shared model: - Faster development - Consistent mappings - Simplified integration logic … all while still preserving each customer’s unique fields, workflows, and schema drift. Instead of flattening complexity into a simplified schema, Ampersand lets you declaratively extend, subscribe to, and transform data in real time. **The result is a flexible unified model that adapts to your product and your customers, rather than forcing your product to adapt to an inelastic schema.** ## When to choose Ampersand over a Unified API Ampersand shines when: - You need depth of service over breadth of integrations (deep, rich, real-time integrations). - Your customers demand enterprise-grade security and reliability to ensure scalability of their services. - You want agents or workflows powered by live data, not fifteen-minute-old snapshots. ## Quick Comparison | **Provider** | **Best For** | **Limitations** | **Example Use Case** | | --- | --- | --- | --- | | Merge | Broad unified API coverage (HR, ATS, CRM, ticketing) | Polling-based sync, hides custom fields, ops burden on you | SMB SaaS needing lots of connectors | | Apideck | Very broad catalog across SaaS categories | Lowest-common-denominator schemas, data freshness issues | SMB SaaS teams launching an integration marketplace quickly | | Unified to | Modern, dev-friendly unified API | Coverage still growing, early-stage ecosystem | SMBs needing fast integrations across core SaaS apps | | Finch | Unified API for employment/payroll data | HR/payroll only, polling-based, narrow use cases | HR tech platforms pulling payroll + benefits data | | Codat | Unified API for accounting and financial data | Finance/accounting only, unified schema constraints | Fintechs and SaaS platforms connecting to SMB accounting systems | | **Ampersand** | Real-time, deep, tenant-specific integrations | Not a unified API (different category) | Enterprise SaaS or AI agents needing live sync across critical Saas apps | ## Going beyond Unified APIs Unified APIs are a great starting point if your priority is breadth of integrations and speed to market. But when your product needs **depth, real-time reliability, and enterprise readiness**, it’s worth looking beyond unified APIs. Ampersand excels in providing foundational integration infrastructure built for highly complex, AI-native applications. Schedule a demo [here](https://calendly.com/d/cmdf-fnw-bwv/speak-with-an-engineer-at-ampersand?utmsource=blog) or [sign up](https://dashboard.withampersand.com/sign-up?utmsource=blog) to begin discovering Ampersand for yourself.
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