Microsoft has released version 0.29 of DevProxy, a command-line tool for simulating APIs. The new version includes AI support for configuring and using the tool.
DevProxy (formerly known as Microsoft 365 Developer Proxy) helps developers to add resilience to their API-related code by simulating a vast number of API and network behaviours. By default, the tool acts as a proxy that fails half the time. It can also simulate throttling, rate-limiting or slow API responses. It can be used to mock responses to specific APIs. Combined with dev tunnels CLI, a ngrok-like tool, it can also inspect cloud services communication to understand what messages are being passed in cloud calls.
To support DevProxy configuration using natural language, the development team has released a MCP server. It allows AI agents such as GitHub Copilot to automatically correctly configure DevProxy for user’s needs. The MCP is exposed via DevProxy Toolkit Visual Studio Code extension or via a standalone npm package called @devproxy/mcp.
DevProxy internally uses language models (LLMs) to generate OpenAPI or TypeSpec files from API call samples. In this release, the prompts that DevProxy uses are exposed in the prompt folder directory where DevProxy is installed. The prompts are saved in Prompty specification format.
The new version brings breaking changes that will require some adjustments for developers building DevProxy plugins. The new architecture uses a different base class coming from DevProxy.Abstractions assembly, with the standard plugins contained in the DevProxy.Plugins assembly.
For troubleshooting issues with the tool, this version includes categories for debug and trace messages, helping developers quickly identify where the error message is originating.
Lastly, when DevProxy is uninstalled, it automatically uninstalls the root certificate that’s installed for decrypting HTTPS traffic.
An updated DevProxy Toolkit extension for Visual Studio Code editor is released together with the tool.
DevProxy is an open-source project on GitHub and a new member of the .NET Foundation non-profit organisation. The complete release notes for this version are available on the site. There are 26 contributors and 53 open issues at the moment. The project has been starred 676 times.
