OrcA: Orchestrator for APIs and Agents
OrcA is the IDE component of the HAPI MCP Stack. It brings the whole API contract → MCP server journey into your editor: it finds your OpenAPI and Arazzo contracts, lets you explore them, previews the MCP tools an agent will get, runs them locally with the HAPI CLI, deploys them, and manages the resulting servers.
OrcA ships as a VS Code extension. See VS Code extension (OrcA) for installation, a quickstart and step-by-step guides.
Why OrcA?
API contracts live in the IDE; MCP servers traditionally live somewhere else. Turning an API into agent tools meant switching between the editor, a terminal, a browser console and the docs, and hoping they still agreed.
OrcA closes that loop:
| Without OrcA | With OrcA |
|---|---|
| Hand-written MCP wrappers for every endpoint | Every OpenAPI operation becomes an MCP tool (via HAPI) |
| Guessing which tools an agent will see | Dry Run shows the exact MCP tool list first |
| Terminal scripts and port juggling to start servers | Run with HAPI picks a free port and tracks the server |
| Separate dashboards to deploy and monitor | Deploy and manage MCP servers from the sidebar |
| Multi-step API calls improvised by the LLM | Arazzo workflows run as one deterministic MCP tool |
The principle is the same as the rest of the stack: your API contract is the source of truth. OrcA adds no code to your API; it helps you author, validate and operate contracts, and delegates execution to HAPI.
Where OrcA fits in the HAPI stack
| Component | Role | Relationship to OrcA |
|---|---|---|
| HAPI Server / CLI | Serves OpenAPI and Arazzo documents as MCP servers | OrcA runs it (hapi serve) and previews it (--dry-run) |
| runMCP | Gateway and hosting for MCP servers | Target of Deploy in remote mode |
| chatMCP | Conversational front end for MCP tools | Consumes the servers OrcA runs or deploys |
| HAPI Workflows | Arazzo workflows as MCP tools | OrcA authors and validates Arazzo 1.1 documents |
What OrcA does
- Contracts: finds every OpenAPI 3.x and Arazzo 1.1 document by content, in your workspace and your HAPI Home.
- Outline: navigates paths, operations, schemas, workflows and steps, and jumps to the exact line.
- Dry Run: previews the MCP tools as JSON (ChatGPT App submission), Markdown (agent system prompt), YAML or a table.
- Run with HAPI: starts a local MCP server on a free port, and tracks it until it stops.
- Deploy and manage: creates MCP servers from OpenAPI contracts, then starts, stops, restarts and deletes them, and shows their logs. Add to VS Code registers a server in
.vscode/mcp.json. - Author Arazzo: Arazzo 1.1 templates, schema validation in the Problems panel, and export.
Details on each concept: How OrcA works.
OrcA and the runMCP extension
OrcA replaces the earlier runMCP VS Code extension, which is deprecated; all of its features are in OrcA. This is unrelated to the runMCP gateway component, which OrcA deploys to.