OrcA — OpenAPI & Arazzo to MCP Server, inside VS Code

OrcA stands for Orchestrator for APIs and Agents. It bridges the gap between your API contracts and MCP servers, all within VS Code.

Turn any OpenAPI (Swagger) or Arazzo contract into a running MCP server, without leaving your editor. OrcA finds your API contracts, lets you explore them, previews the exact MCP tools an AI agent will get, runs them locally, and deploys them. It is powered by HAPI, the headless API engine of the HAPI MCP Stack.

API contract in, MCP tools out. No glue code, no SDK, no context switching between editor, terminal, browser and docs.

Why OrcA?

Your API contracts live in your IDE. Your MCP servers live somewhere else. Every change means switching between the editor, a terminal, a browser console and the docs, and hoping they still agree.

OrcA puts the whole loop in one place:

Without OrcA	With OrcA
Hand-write MCP tool wrappers for every endpoint	Every OpenAPI operation becomes an MCP tool automatically
Guess what tools an agent will see	Dry Run shows the exact MCP `tools/list` before you ship
Terminal scripts to start a server	Run with HAPI: one click, from the editor title bar
Separate dashboards to deploy and monitor	Deploy and manage MCP servers from the sidebar
Multi-step API calls left to the LLM to improvise	Arazzo workflows run as one deterministic MCP tool

Features

🔎 Contracts: every OpenAPI and Arazzo file, found for you

OrcA recognizes contracts by their content (openapi: 3.x, arazzo: 1.1), not only by their file names. It groups them by where they live:

Workspace: the folders you have open.
HAPI Home: your personal spec library (~/.hapi/specs).

Start a new contract from a clean OpenAPI 3.1 or Arazzo 1.1 template with New Contract….

🧭 Outline that follows your file

Open any contract and the Outline mirrors it:

OpenAPI / Swagger: paths → operations (colored by HTTP method), schemas and properties, security schemes, servers, tags, and x-hapi metadata.
Arazzo: source descriptions, workflows → steps, success criteria, outputs and components.

Click any node to jump to its exact line, even in large specs. You can add or remove Arazzo sources, workflows and steps from the tree, and undo the change.

🧪 Dry Run: see the MCP tools before you serve them

Preview what an AI agent will get, in the format you need:

JSON: a ChatGPT App submission dump, ready to complete.
Markdown: an AI-agent system prompt template built from your tools.
YAML or a readable table.

The result opens beside your contract. Nothing is started, and nothing is deployed.

▶️ Run with HAPI: a local MCP server in one click

Run hapi serve for any OpenAPI or Arazzo contract in an integrated terminal. Run with Options… adds headless (MCP-only) mode, development mode (hot reload), or a custom port. Paths with spaces are handled on Linux, macOS and Windows.

☁️ Deploy and manage MCP servers

Deploy MCP Server from any OpenAPI contract: just name the server. Your HAPI profile decides where it runs and on which plan.
MCP Servers view: running and stopped servers, with start, stop, restart, logs, open in browser, and delete.
Add to VS Code: register a running server in .vscode/mcp.json with one click, so Copilot, Claude and other MCP clients in VS Code can use it right away.

🏠 HAPI Home

Browse the folders the hapi CLI uses (specs, config, plugins, logs, certs) and run, dry-run or deploy the specs stored there. Private keys are never previewed without your confirmation.

✅ Arazzo workflow authoring

Arazzo 1.1 schema validation in the Problems panel, Validate All across your workspace, export to JSON or YAML, and custom deployment hooks.

🔔 Activity, status and guidance

Activity (Secondary Sidebar): a timeline of server events.
Status bar: your HAPI session and mode (local or remote).
OrcA Guide: an animated tour plus built-in docs, available offline.
Get started with OrcA: a walkthrough on the VS Code Welcome page.

How to

Turn an OpenAPI spec into MCP tools in 60 seconds

Open your openapi.yaml (or create one with OrcA: New Contract…).
Click Dry Run in the editor title bar and choose Table to see the MCP tools.
Click Run with HAPI. Your MCP server is now running on http://localhost:3000/mcp.
In MCP Servers, use Add to VS Code to connect it to your AI assistant.

Generate an AI-agent system prompt from an API Run Dry Run → Markdown. You get a prompt template with every tool already listed; complete the role and policies with your favorite coding agent.

Prepare a ChatGPT App submission Run Dry Run → JSON. The tool names, descriptions and read-only/destructive hints are filled in from your contract.

Orchestrate multiple API calls deterministically Create an Arazzo workflow (New Contract… → Arazzo Workflow), describe the steps, and run it with HAPI. The whole workflow is exposed as a single MCP tool.

Requirements

VS Code 1.138 or newer (Windows, macOS, Linux, WSL, SSH and Dev Containers).
The HAPI CLI for Run and Dry Run. Don't have it? OrcA offers to install it in one click (OrcA: Install HAPI CLI).

Privacy

In the default local mode, OrcA makes no network calls; your contracts and servers stay on your machine. Remote mode talks only to the HAPI API you configure, and sign-in tokens are kept in VS Code's secure secret storage.

Frequently asked questions

Does OrcA support Swagger 2.0? OrcA works with OpenAPI 3.x. Convert Swagger 2.0 documents to OpenAPI 3 first; OrcA tells you when a file is Swagger 2.0.

What is Arazzo? Arazzo is the OpenAPI Initiative's specification for describing sequences of API calls (workflows). OrcA writes and validates Arazzo 1.1.

Which MCP clients can use the servers? Any client that speaks the Model Context Protocol over HTTP, including VS Code (GitHub Copilot), Claude, ChatGPT Apps, and your own agents.

Learn more

OrcA is part of the HAPI MCP Stack by La Rebelion Labs. Be HAPI, and enjoy building!

OrcA: OpenAPI & Arazzo to MCP Server

La Rebelion Labs