Introduction

In today's digital landscape, businesses are driven by APIs. Whether you're building a public-facing SaaS platform or modernizing legacy systems, your API is the contract between your services and the outside world. At Assemblysoft, we help organizations of all sizes design, implement, and operate Web APIs that are secure, scalable, and built to last.

Through our custom software development services, we partner with you to deliver APIs that meet your unique needs—adhering to RESTful principles, enabling platform independence, and ensuring long-term maintainability. This article explores our API-first approach, featuring best practices, real-world tooling, and how our UK-based development team can help you succeed.

Why Design-First Matters

We believe in treating your API like a product. That means following a design-first approach using OpenAPI specifications. Before a single line of backend code is written, our developers and stakeholders agree on the API contract. This reduces friction, supports parallel development, and enables a better developer experience for consumers.

At Assemblysoft, every API we build starts with:

OpenAPI-driven design

API contract validation in CI/CD pipelines

Mocking with tools like Prism or Stoplight

Clear versioning and lifecycle documentation

Seamless integration with Azure API Management (APIM)

Learn more about our fullstack Blazor development and API integration expertise.

The 15 Golden Rules of Web API Operations

Assemblysoft’s API projects follow a battle-tested playbook. Here are just a few highlights:

Treat API Specs as Code – All contracts live in Git, reviewed via pull requests.

Validate OpenAPI Automatically – Catch errors early with CI linting tools like Spectral.

Automate Everything – From deployment to policy rollout via GitHub Actions or Azure DevOps.

Mock Early, Integrate Late – Empower front-end teams with mock servers before backends are ready.

Publish Consistently – We automate API documentation publication using SwaggerHub or ReDoc.

Monitor Usage and Performance – Observability is built-in using Azure Monitor or OpenTelemetry.

Scan for Vulnerabilities – Secure your APIs with tools like OWASP ZAP or Snyk during every build.

Canary & Blue/Green Releases – Deploy with confidence and roll back instantly if needed.

We don’t just build APIs—we help govern them through metadata standards, developer portals, and consumer feedback loops.

RESTful Design Done Right

Following industry standards and the Richardson Maturity Model, we target Level 3 maturity where appropriate. Our approach includes:

Clean, consistent URI design (e.g., /customers/123/orders)

Proper HTTP verb usage (GET, POST, PUT, PATCH, DELETE)

Support for content negotiation (JSON, XML)

Pagination, filtering, sorting, and projection query support

Asynchronous operation handling with polling and status endpoints

Versioning via URI, headers, or media types

Multitenancy using subdomains, headers, or claims

We also support HATEOAS where applicable, helping clients understand the "what's next" of your API.

Tools We Use to Power Your APIs

Assemblysoft leverages industry-leading tools to streamline API development and testing:

🛠️ Design: Swagger Editor, Stoplight Studio, Postman API Builder

🔐 Security: Azure API Management, Azure Key Vault, OAuth2, IdentityServer

🔬 Testing: Postman, Dredd, FluentAssertions, Playwright

🌍 .NET Integration: Swashbuckle, NSwag, JWT middleware, OpenTelemetry

We don’t just recommend tools—we use them every day to build and maintain robust APIs for our clients.

Your API, Built to Last

Working with Assemblysoft means more than just code delivery. We ensure:

Secure-by-default APIs with OAuth2, HTTPS, and token validation

Documentation that is versioned, published, and consumer-friendly

CI/CD pipelines that test, validate, and deploy across environments

Observability through logs, tracing, and health endpoints

Lifecycle governance for versioning, deprecation, and retirement

Check out how our clients are succeeding with modern, maintainable APIs by visiting assemblysoft.com.

Ready to Build Your API?

Whether you're launching a new product or modernizing a monolith, Assemblysoft brings deep expertise in Web API design and delivery. Our UK-based team is ready to guide your project from concept to production with proven best practices and real-world results.

Let us help you design APIs that developers love and businesses can rely on.

Contact Assemblysoft today to start your API journey with confidence.