If your marketing team runs on HubSpot but half your data lives in systems HubSpot doesn't natively connect to, you already know the problem. Deals slip through gaps between your CRM and your ERP, billing platform, or proprietary database. A custom HubSpot integration agency can close those gaps, but only if you pick one with the right technical capabilities.
HubBase has built over 100 custom integrations connecting HubSpot to platforms that lack native connectors. That experience has given us a clear picture of what separates agencies that deliver reliable integrations from those that create more problems than they solve.
This article walks you through the specific capabilities you should evaluate before signing with any integration partner.
Your integration partner needs hands-on experience building custom APIs that connect HubSpot to systems without existing marketplace connectors. This includes working with both REST and SOAP protocols, managing OAuth authentication flows, and handling token refresh logic reliably across production environments.
Ask to see examples of integrations they've built with proprietary or legacy systems. An experienced agency will explain their approach to API rate limiting, error handling, retry mechanisms, and data validation without you having to prompt them for those specific details.
HubSpot's native objects cover standard CRM use cases. But mid-market teams often need to track data types that don't fit neatly into contacts, companies, or deals. A capable integration agency should demonstrate fluency in creating and managing custom objects and their property schemas.
This means defining object schemas, configuring multi-level associations between objects, and building automation that triggers based on custom object property changes. If your agency can't clearly articulate how they handle custom object relationships and association labels, they likely lack the depth your project demands.
CRM extensions allow your team to view and interact with external data directly inside HubSpot records without switching between applications. A qualified agency should know how to build React-based UI extensions that pull live data from your external systems into the CRM interface in real time.
Ask whether they've built custom CRM cards or UI extensions for production environments. These require a HubSpot Enterprise subscription and deep familiarity with HubSpot's developer platform, including frontend rendering, serverless functions, and secure data fetching patterns.
Standard workflow actions cover common automation scenarios. But when you need HubSpot to trigger actions in external systems or process data through custom business logic before returning results back to the workflow, you need custom workflow actions built by experienced developers.
Look for an agency that has built and deployed custom workflow actions that extend HubSpot's automation capabilities beyond what the platform offers natively. These actions should handle timeout scenarios, error states, callback patterns, input validation, and logging cleanly across all edge cases.
One-way data pushes are relatively straightforward to implement. Bidirectional sync, where changes in either system update the other, introduces real complexity around conflict resolution, data deduplication, and maintaining integrity across both platforms simultaneously during high-volume operations.
A strong agency will describe their specific approach to handling race conditions, managing webhook reliability (HubSpot retries failed deliveries for 24 hours), and running nightly reconciliation jobs that catch any data drift. If they haven't built reconciliation logic before, they'll be learning on your project at your expense.
Integration work involves moving sensitive data between systems, often including customer records, financial information, or health data. Your agency should follow defensive coding practices, encrypt data in transit and at rest, and understand the compliance frameworks relevant to your industry, including HIPAA, GDPR, and SOC 2.
HubBase applies security-first development standards including penetration testing and thorough code audits to every integration project. Ask any prospective partner about their specific security review process and whether they've completed projects in regulated environments before.
HubSpot's Custom Integration Accreditation validates that an agency has demonstrated advanced expertise in building integrations through real client implementations and a rigorous multi-step review process. This is fundamentally different from basic platform certifications, which only require passing knowledge exams without evidence of client work.
Also check for CMS certifications, Data Integration credentials, and partner tier status. While tier alone doesn't guarantee project quality, accreditation specific to integrations signals hands-on experience that has been verified directly by the HubSpot partner team through documented client evidence.
Integrations aren't set-and-forget. APIs change, HubSpot releases platform updates regularly, and your own business requirements will evolve over time. Evaluate whether the agency offers ongoing support with clear SLAs for response times, issue resolution, proactive monitoring, and scheduled maintenance windows for updates.
HubBase includes ongoing monitoring and maintenance for the integrations they build, including proactive updates when HubSpot's API changes affect your workflows. Get these support terms documented in your contract before you sign to avoid surprises and disputes later.
A well-built integration should come with documentation that your internal team can reference without calling the agency for every question. Look for partners who deliver architecture diagrams, detailed field mapping documents, runbooks for common maintenance tasks, and troubleshooting guides for known edge cases.
Good documentation reduces your long-term dependency on the agency and helps new team members onboard faster. It also makes future HubSpot integration projects easier to scope because your existing architecture is already well-documented and accessible to your entire team.
Generic case studies with vague outcome statements aren't enough. Ask for specific examples of integrations involving systems similar to yours in both complexity and data volume. A partner who has connected HubSpot to your specific ERP, database type, or industry vertical will anticipate problems that less experienced teams miss entirely.
Request references you can speak with directly. Ask those references about communication quality, timeline accuracy, how the agency handled unexpected issues during the project, and whether the delivered integration performed reliably after launch without needing constant manual intervention.
Selecting the right integration partner comes down to matching technical capabilities with your specific requirements. Start by listing the systems you need connected, the data flows you require, and any compliance constraints. Then evaluate agencies against the ten criteria above.
HubBase gives you a team of HubSpot-certified developers with 14 years of platform experience and over 100 completed custom integrations. If you need an agency that handles custom APIs, workflow actions, CRM extensions, and ongoing maintenance under one roof, schedule a free consultation to discuss your project.
HubSpot's Custom Integration Accreditation verifies that an agency has demonstrated advanced expertise in building custom integrations through real client projects. It requires passing a rigorous review process, not just a certification exam.
Simple one-way syncs typically ship in one to two weeks. Bidirectional integrations with conflict resolution take four to eight weeks. Full marketplace apps with OAuth and UI extensions may require three to six months.
Basic API access works on HubSpot's free tier. Custom objects, advanced webhooks, and CRM UI extensions for production use require Professional or Enterprise subscriptions. HubBase helps you determine which tier fits your needs.
Native connectors are pre-built apps in HubSpot's marketplace designed for standard use cases. Custom integrations are built specifically for your business logic, data flows, and systems that lack native support.
Ask for case studies with specific metrics from projects similar to yours. Request a technical discovery call where they explain their approach to error handling, webhook reliability, and data reconciliation. HubBase offers free consultations with a technical assessment included.
Plan for monitoring, periodic API updates, and edge case resolution. Most integrations need a few engineering hours monthly for maintenance. HubBase offers support plans that cover ongoing maintenance so your integrations stay reliable.