A CRM API Built for Developers Who Ship Fast

What Is a CRM API?

A CRM API (Application Programming Interface) is a set of endpoints that allow external software to access, create, update, and delete data in your CRM programmatically. Instead of interacting with your CRM exclusively through the user interface, an API enables developers to build custom integrations, automated workflows, and applications that interact with CRM data directly.

APIs are essential for businesses that need their CRM to work as part of a larger technology stack. Whether you are building a custom dashboard, syncing data with an ERP or accounting system, automating processes that go beyond the standard UI, or embedding CRM functionality into another application, the API is the gateway that makes it possible.

A good CRM API is well-documented, versioned, predictable, and gives you access to the same data and operations available in the user interface. It should feel like a first-class product feature, not an afterthought bolted on for enterprise customers.

How the CRM API Works in Customermates

Customermates provides a versioned REST API for documented CRM resources and operations. API access is included in published pricing tiers from €12 per user per month, without a separate developer tier.

REST architecture with predictable endpoints. The API follows standard REST conventions with predictable URL structures, standard HTTP methods (GET, POST, PUT, PATCH, DELETE), and JSON request and response bodies. If you have worked with any modern REST API, working with the Customermates API will feel familiar immediately. Endpoints follow a consistent pattern: /api/v1/{resource} for collections and /api/v1/{resource}/{id} for individual records.

Documented operations by resource. Create, read, update, or delete only where the current OpenAPI document exposes that operation. Availability differs by resource; do not assume complete UI/API feature parity.

OpenAPI specification. The API is documented with a complete OpenAPI 3.1 specification, available at /api/v1/openapi. Import the spec into Postman, Insomnia, or any API client to explore endpoints interactively. Use the spec to auto-generate client libraries in any programming language.

MCP endpoint for supported external AI clients. Customermates exposes 46 MCP tools for allowed CRM and messaging operations, authenticated by API key or OAuth bearer token depending on the client flow. Supported clients such as Claude, ChatGPT, or Gemini remain external; Customermates includes neither the client nor an AI model.

Filtering, sorting, and pagination. Use the supported filter and sort parameters for each resource. Multiple user-facing filter conditions combine with AND, and generic list endpoints use page and pageSize; top-level OR and cursor pagination are not supported.

Authentication via API keys. Authenticate API requests using secure API keys generated from your account settings. Keys can be created and revoked at any time. Each key inherits the permissions of the user who created it, ensuring that API access respects your existing role-based access control.

Webhooks for real-time event streaming. Configure webhooks to receive real-time HTTP POST notifications when events occur in your CRM. Customermates emits 26 webhook events: 15 record events (created, updated, and deleted for each of the five entities: contacts, organizations, deals, services, tasks) plus 11 messaging and calendar events. Any of them can trigger a delivery to a URL you specify. Webhooks include retry logic with exponential backoff for failed deliveries.

Supported custom-field access. Read or write custom-field values only where the documented resource and operation expose them. Treat the current OpenAPI document, field types, and validation responses as the integration contract.

Large data operations through integrations. Customermates has no built-in CSV importer, exporter, or generic batch endpoint. A customer-run integration can create or update supported records through documented API calls and owns batching, validation, mapping, deduplication, and retries.

Endpoint behavior. Follow the current API documentation and responses when planning throughput and retries. Customermates does not publish a generic application rate-limit quota or rate-limit headers for this API surface.

Versioned API. Routes live under /api/v1. Treat the current OpenAPI document as the contract; no indefinite backward-compatibility promise or fixed deprecation timeline is made here.

Key Benefits

External AI clients operate allowed CRM data. A supported client can use MCP tools to create records, update deal stages, and draft individual follow-ups where permitted. Customermates supplies the MCP surface, not the AI client, model, subscription, or autonomous outcome.

Build on documented CRM operations. Use the API for custom dashboards, mobile apps, partner portals, customer-facing tools, and internal automation scripts when the documented resources and operations meet your requirements.

Automate beyond the UI with code or a separate n8n instance. Use your own n8n instance for visual workflows or the API for custom scripts. Customermates publishes integration interfaces and a community node; the n8n runtime, plan, logs, limits, and costs remain separate.

Sync data across your entire tech stack. Keep your CRM data consistent with ERP systems, accounting software, marketing platforms, support desks, and data warehouses. The API and webhooks together enable both push and pull synchronization patterns for real-time or scheduled data flows.

Embed CRM data in custom applications. Build internal tools, customer portals, or partner dashboards that pull CRM data in real time. The API enables any application to become CRM-aware without requiring users to switch contexts.

Developer-friendly from day one. Standard REST conventions, JSON, an OpenAPI spec, and documented responses give developers a familiar starting point. Follow the current API contract for authentication, supported operations, pagination, and errors.

Open-source transparency. Because Customermates is open source, the API implementation is fully inspectable. Developers can read the source code behind any endpoint, understand exactly how it works, and even contribute improvements upstream.

Common CRM API Use Cases

Custom dashboard and reporting. Build internal dashboards that combine CRM data with data from other systems. Pull pipeline metrics, activity counts, revenue figures, and conversion rates through the API and display them in a custom interface tailored to your management team.

Website and form integration. When a visitor submits an external form, use the API to create supported CRM records. Map form fields to supported CRM fields; calculate lead scores or routing in the external integration, then write approved values back where the documented API permits.

Data migration from other CRMs. Prepare and map source data outside Customermates, then create supported records through a customer-run API integration. There is no built-in import workflow; your integration owns batching, validation, field mapping, deduplication, and transformation.

ERP and accounting system sync. Sync deal data with your ERP or accounting software. When a deal is won, push invoice data to your billing system. When a payment is received, update the deal status in the CRM. Two-way sync keeps both systems accurate.

Webhook-driven workflow orchestration. Use webhooks to trigger external processes when documented CRM events occur. When a deal is won, trigger provisioning in your product. When a contact is updated, sync supported changes. When a customer-defined task date needs attention, let an external scheduler evaluate that custom field and send a Slack notification through an external provider; Customermates has no native task due or overdue state.

Mobile and desktop applications. Build custom mobile or desktop applications that access CRM data through the API. Sales teams in the field can access and update records through purpose-built interfaces optimized for their specific workflow.

Data enrichment pipelines. Enrich CRM contacts with data from third-party providers. Use the API to read contacts, call enrichment services, and write the enhanced data back. Automate the pipeline to run on a schedule or trigger it via webhooks when new contacts are created.

Testing and development with sandbox data. Use the API to seed test environments with realistic CRM data. Build automated test suites that create, modify, and verify CRM records to ensure your integrations work correctly before deploying to production.

Why Choose Customermates for API Access

Open source and fully transparent. The API is part of the open-source Customermates codebase. Inspect the implementation, understand the data model, and contribute improvements. No black-box API behavior.

EU database region with documented providers. The hosted database runs in an EU region. Application hosting and other providers, including US providers, are documented separately; this is not a GDPR or other compliance certification.

Simple, published pricing. Documented API access is included in published plans from €12 per user per month. Follow the current API documentation for supported operations and applicable boundaries; no undocumented unlimited-use or full-parity promise is made.

Self-hostable application and database. When self-hosted, the Customermates application and PostgreSQL database run on your infrastructure. External services you connect remain separate, so deployment location alone does not establish security or compliance.

Webhook reliability with retry logic. Webhook deliveries include automatic retries with exponential backoff for failed deliveries. Delivery logs let you inspect the payload and response for every webhook event, making debugging straightforward.

Separate n8n for hybrid workflows. Combine API access with an n8n instance you operate. Customermates does not bundle n8n; its subscription, hosting, connectors, limits, logs, and usage costs remain yours.

Get Started with the CRM API Today

Start building with the Customermates API. Generate an API key in account settings, explore the OpenAPI spec, and make your first request. Use the current OpenAPI spec to confirm supported resources and operations for your integration. Documented API access is included from €12 per user per month.