MockServer vs WSO2 API Designer

MockServer is a free, self-hosted tool for mocking and proxying HTTP, HTTPS, and gRPC services during isolated testing. It can verify requests as well as stand in for services. Teams can generate mocks and validate traffic against OpenAPI or Swagger contracts, or import recorded sessions from browser HAR files and Postman collections. Beyond HTTP services, it can mock gRPC, AsyncAPI brokers such as Kafka, MQTT, and AMQP, and OAuth2/OIDC providers. Its protocol coverage includes HTTP/1.1, HTTP/2, HTTPS, SOCKS, and experimental HTTP/3, which uses a separate UDP port. For fault-oriented testing, it can add latency, errors, dropped connections, and malformed responses to mocked or proxied traffic. Deployment options include Docker, an executable JAR, Helm/Kubernetes, Testcontainers, Homebrew, and a JVM-less bundle. A web dashboard displays logs, expectations, and recorded traffic; Prometheus metrics and OpenTelemetry tracing are available for shared environments. Each instance includes an MCP server at /mockserver/mcp. The /mockserver/status and /mockserver/ready probes remain reachable without authentication or authorization.

WSO2 API Designer is a Visual Studio Code extension for creating and refining OpenAPI 3.x specifications in YAML or JSON. Its design view presents API resources, operations, and reusable components, with form-based editing for operations and schemas. An API Design Skill can draft specifications from prompts with GitHub Copilot; Copilot is optional. The extension checks specifications against bundled Spectral rulesets for WSO2 AI readiness, WSO2 REST API design guidelines, and the OWASP API Security Top 10. AI-assisted analysis adds narrative feedback to rule-based findings, including issues that may affect agents and tools. Users can also point it to custom rules in a GitHub folder or an absolute local directory. Installation is available through the VS Code Marketplace, with documented compatibility for extension engine requirement ^1.100.0. WSO2 directs users to its official Discord community for discussion and help. API Designer is available in a free 30-Day Trial with limits of 5 Managed Interfaces and 10M Gateway Events. Growth costs $119 a month. Enterprise pricing is custom and not listed. WSO2 warns that security checks may need real URLs, policies, or authorization-server metadata; AI should not invent production values.