ApyHub Built a System to Let AI Agents Run and Test APIs Directly from Code

ApyHub, a utility API catalog, found itself maintaining two separate API descriptions after building an MCP server to let AI assistants like Claude and ChatGPT call its APIs directly. The team identified three distinct problems stemming from this duplication: agents lacking direct access to existing requests during debugging, manual MCP server creation causing API definitions to drift out of sync, and no reliable way to gate agent access based on test status. To address this, they developed a workflow using their open-source tool Voiden, which stores API requests as plain Markdown files and allows coding agents to list, run, and inspect real endpoints without manual re-description. They also introduced an opt-in model where existing tested requests are simply marked as tools, keeping secrets in the environment and exposing nothing by default. A key design choice ties tool availability to test results — if a test fails, the corresponding agent tool goes offline — a strict tradeoff the team acknowledges is still open for debate.