# Four Echelon API

> Two endpoints. Four Cad turns a CAD file or drawing into structured JSON; Rowe reasons over that structure and returns typed spatial output. Everything else on this site is a surface over those two calls.

Source: https://fourechelon.com/docs · Machine-readable: https://fourechelon.com/openapi.json · Index: https://fourechelon.com/llms.txt

## The two calls

- `POST /api/v1/cad/extract` (Four Cad): upload STEP, IGES, DXF, PDF, SVG, or draw.io; get `four-cad.extraction.v1` back.
- `POST /api/v1/responses` (Rowe 1.0): send a `cad_scene` or `point_cloud_scene` with a `task_type`; get typed spatial output, usage, and a `request_id`.

## Supported today

| Format | Status | Detail |
| --- | --- | --- |
| STEP / STP | supported | 3D solids, faces, exact volumes |
| IGES / IGS | supported | 3D solids and surfaces |
| DXF | supported | 2D entities, dimensions, annotations |
| PDF | supported | Vector drawing entities and annotations |
| SVG | supported | Vector drawing entities |
| draw.io (.drawio / .xml) | supported | Diagram nodes with absolute geometry, containers, connectors with direction, spatial relations |
| OBJ / STL / JSON | supported | Point clouds and meshes, browser-side |

## Not supported (stated up front)

| Item | Status | Detail |
| --- | --- | --- |
| SolidWorks native (.sldprt / .sldasm) | not supported | Export to STEP and upload that. The API returns HTTP 415 — deliberately, not as a bug. |
| Latency SLAs | not supported | The status page reports single-probe latency samples. We do not publish p50/p99 guarantees. |
| Head-to-head accuracy claims | not supported | We publish our own eval methodology, every scoring condition, and error bars. We do not claim to be best, superior, or state of the art. |
| Diagram formats other than draw.io | not supported | Visio, Lucidchart, and Mermaid have no parser and no normalized contract today. draw.io (.drawio / .xml) is live; the rest are on the roadmap, not shipped. |

## Machine-readable

- OpenAPI 3.1: https://fourechelon.com/openapi.json
- Markdown for any page: append `.md` to its URL (for example https://fourechelon.com/docs/cad-extract.md)
- Index for agents: https://fourechelon.com/llms.txt and https://fourechelon.com/llms-full.txt
- MCP server: POST https://fourechelon.com/api/mcp (see /docs/mcp)
- SDKs: `npm install fourechelon`, `pip install fourechelon` (see /docs/sdks)
- Agent Skills: `npx skills add https://fourechelon.com` (index at /.well-known/skills/index.json)