# Craggy Modeller

> A visual editor for block models: labelled areas nested by containment, labelled relationships between them, typed properties and cited evidence, stored as one JSON format ("craggy.model", version 2). Agents use it through an MCP server; people view and edit the result in the browser.

## Use it from an agent

The MCP server is at https://models.craggy.io/mcp (streamable HTTP, stateless, no accounts). Nothing is stored: the agent keeps the model document and passes it to each tool.

- Claude Code: `claude mcp add --transport http craggy-models https://models.craggy.io/mcp`
- Any MCP client: `{"mcpServers": {"craggy-models": {"type": "http", "url": "https://models.craggy.io/mcp"}}}`
- Local over stdio: `go install github.com/craggy-io/modelling-services/cmd/modelling-mcp@latest`, then run `modelling-mcp`

Tools: model_import (outline, Mermaid or CSV to a document), model_check (validate and lint), model_apply (small invertible edits), model_diff, model_query (neighbours, paths, impact, search), model_export (outline, Mermaid, DOT, SVG, CSV) and model_open (a link that opens the model here).

A quick start: write a Markdown outline, import it, refine with model_apply, then give the user the model_open link.

```markdown
# Payment app

com.example.pay

- **Application** `app`
  - **UI layer** `ui`
  - **Network layer** `net`
- **Payment API** `api`

## Relationships

- `ui` -> `net`: calls `ui--net`
- `net` -> `api`: posts payments to `net--api`
```

## Open a model without the MCP server

https://models.craggy.io/#m=DATA opens a model, where DATA is the canonical JSON document, compressed with raw DEFLATE (no zlib header) and base64url-encoded without padding. The fragment never reaches the server.

## Reference

- [MCP server](https://github.com/craggy-io/modelling-services/blob/main/docs/mcp.md): tools, clients, hosting
- [Format](https://github.com/craggy-io/modelling-services/blob/main/docs/format.md): the document format
- [JSON Schema](https://models.craggy.io/schema/model.v2.schema.json): format version 2
- [Edit operations](https://github.com/craggy-io/modelling-services/blob/main/docs/edit.md)
- [Source](https://github.com/craggy-io/modelling-services)