Most of the API clients we tried over the years started as simple request runners and slowly turned into cloud platforms. Every new protocol behind a paywall. Every account prompt. Every “your data is being synced to our servers” disclaimer. We started asking: why is the tool that's supposed to help us test our APIs so dependent on the cloud?
The moment things changed
It wasn't one thing. It was a slow accumulation. The first time we lost a collection because an account got rate-limited mid-demo. The first time we discovered that pre-request scripts had a cap we didn't know about. The first time a teammate on a slow hotel Wi-Fi couldn't sync their environment variables before a critical call.
We're a small team that works across time zones, often without reliable internet. We needed a tool that worked the same in an airport lounge as it did in the office — one built for a laptop, not for a server.
What we actually needed
When we wrote down what an ideal tool would look like, we ended up with a list that felt unreasonable:
- Every protocol we use — HTTP, WebSocket, gRPC, GraphQL, MQTT — all in one place, all for free
- Scripting that runs locally, not on a server somewhere
- Collections that live on disk, as files, so we can Git-version them like everything else
- No account required to access basic features
- An AI assistant that could use a local model so our API design never touches an external server
None of these seemed unreasonable individually. Together, no tool offered them. So we built Rostyman.
What we got right and what surprised us
The core — HTTP requests, environments, collections — went quickly. Electron + React + SQLite is a stack we knew. The hard parts were the protocols. gRPC required building a proto parser and a streaming response handler from scratch. WebSocket required threading a persistent connection through Electron's multi-process architecture without blocking the UI. MCP — the Model Context Protocol from Anthropic — required us to implement a full tool-and-resource server so AI agents like Claude Desktop can browse and execute your API collections.
The thing that surprised us most was how much people wanted local file sharing. We added it because we needed it — dropping a collection or a config file to a teammate's machine over the LAN without Slack or email. It turned into one of the most-used features in early testing.
Where we're going
Next up are Hooks (pre/post-request triggers at the workspace level), Cloud Sync for teams who want it (opt-in, account-required, Pro tier), and eventually a full database client and browser automation layer. The goal is for Rostyman to be the tool you open first, not the tool you reach for when your other tools don't quite cover a case.
We're in beta. It's not perfect. But it's honest, it's fast, and it's yours — it runs on your machine, your data never leaves unless you explicitly want it to, and every core feature is free.
That's what we set out to build. We think we got close.