# Caliper — caliper.fit

> Geometry and CAD file metadata extraction. Accepts geometry files by URL or base64, returns structured statistics as JSON. Payment required via x402 (USDC on Base).

## What This Service Does

Caliper accepts 3D geometry files and returns structured JSON metadata:
bounding boxes, triangle counts, surface area, volume, manifold analysis,
point cloud statistics, classification counts, and more.

## Supported Formats

STL, OBJ, PLY, PCD, LAS / LAZ, glTF / GLB.
STEP and IGES support is planned.

## How to Connect

### MCP Transport (recommended for MCP-compatible agents)

Connect via Streamable HTTP at:
```
https://caliper.fit/mcp/
```

This provides tool discovery (`tools/list`) and direct invocation
(`tools/call`) using the standard MCP protocol.

### REST API (payment required)

POST to `/tools/caliper_auto_stats` (or a format-specific endpoint):
```json
{"file_url": "https://example.com/model.stl"}
```
or:
```json
{"file_b64": "<base64-encoded file>", "filename": "model.stl"}
```

For multiple files, use `/tools/caliper_batch_stats`:
```json
{"files": [{"file_url": "https://example.com/part1.stl"}, {"file_b64": "...", "filename": "part2.obj"}]}
```

REST endpoints require x402 payment (USDC on Base). The server returns
HTTP 402 with payment details; send USDC to the specified address and
retry with the transaction hash in the `X-Payment` header.
Batch requests use a single payment for all files.

## Tools Available

- `caliper_detect_format` — Detect the geometry file format from a filename or URL.
- `caliper_auto_stats` — Auto-detect geometry file format and extract metadata statistics.
- `caliper_stl_stats` — Extract metadata from an STL file (ASCII or binary).
- `caliper_obj_stats` — Extract metadata from an OBJ file.
- `caliper_ply_stats` — Extract metadata from a PLY file (ASCII or binary).
- `caliper_pcd_stats` — Extract metadata from a PCD point cloud file.
- `caliper_las_stats` — Extract metadata from a LAS or LAZ point cloud file.
- `caliper_gltf_stats` — Extract metadata from a glTF or GLB file.
- `caliper_batch_stats` — Analyze multiple geometry files in a single batch request.

## Input Constraints

- `file_url`: HTTP/S only, max 100MB, no private/loopback IPs
- `file_b64`: max 200KB decoded (use `file_url` for larger files)
- Include `filename` with extension for format detection when using `file_b64`

## Discovery Endpoints

- `GET /mcp/manifest` — MCP tool manifest (JSON)
- `GET /.well-known/mcp/server-card.json` — MCP server card
- `GET /.well-known/mcp.json` — MCP discovery manifest
- `GET /llms.txt` — LLM-friendly index
- `GET /health` — service status