# behaviour.write

> Talos next · Since next

[editor or disk] Write a TypeScript behaviour to scenes/behaviors/<name>.ts beside the scene, landed only if the build's type checker passes it; else NOTHING is written and the answer has the diagnostics.

attach_to attaches it and runs the critic. Imports: types from "@argus/api", helpers from "@argus/gameplay", the project's files by relative path; nothing else. example.behaviour gives one that compiles. path instead of name: a ui/ file, checked for its kind. Change an existing file with edits, not source.

| | |
|---|---|
| Title | Write a behaviour |
| Mode |  |
| Token cost | about 548 tokens (in the default list, paid on every call) |
| Toolset | core |

## Arguments

| Argument | Type | Required | Default | Allowed values | Description |
|---|---|---|---|---|---|
| `agent` | `string` | no |  |  | The name of the agent making the call, when several agents share one connection: each named agent is its own actor and plays its own game. Leave it out when there is one agent. |
| `attach_to` | `string` | no |  |  | An entity id; one undo step |
| `delete` | `boolean` | no |  |  | Remove name or path (a ui/, scene, model or data file); revert undoes; refused while referenced |
| `dryRun` | `boolean` | no |  |  | With run: diff only |
| `edits` | `object[]` | no |  |  | [{old, new, replaceAll?}] on an existing file: old exact, unique unless replaceAll; in order, all or none, then checked |
| `files` | `object[]` | no |  |  | Up to 32 {name\|path, source\|edits\|delete: true, attach_to?, props?, overwrite?}; deletes after writes; a result each |
| `name` | `string` | no |  |  | No path or extension; the module is behaviors/<name> |
| `onEdited` |  | no |  |  | With run: keep or overwrite hand-edited owned entities (else refused); or {id: …} |
| `overwrite` | `boolean` | no | `false` |  |  |
| `path` | `string` | no |  |  | Instead of name: ui/{screens/**.tsx, styles/**.css, theme/**.css, locales/<locale>.json, scenarios/**.json}, authoring/<name>.ts (builds entities from data), data/**.json\|csv, selftest/<name>.json |
| `props` | `object` | no |  |  | Its settings, with attach_to |
| `run` | `boolean \| string` | no |  |  | Run the authoring script written (true) or named; it replaces its <name>:* entities as one change |
| `scene` | `string` | no |  |  | The scene file to act on. The open scene when absent. |
| `source` | `string` | no |  |  | A new file's whole module, at most 256 KiB, default-exporting a Behavior |

## Example

An MCP `tools/call` with the required arguments (placeholders in angle brackets).

```json
{
  "name": "behaviour.write",
  "arguments": {}
}
```