Write

Write content to a file on the local filesystem.

Package: @agentrail/capabilities

Parameters

Name	Type	Required	Description
file_path	string	Yes	Absolute path of the file to write.
contents	string	Yes	Content to write. Overwrites the entire file if it exists.

Result

On success:

{
  file_path: string;
}

On error, details contains { error: string }.

Parent directories are created automatically (mkdir -p semantics).

Permissions

Write has a checkPermissions hook that:

1. Rejects paths that fail safety checks.
2. If a rootDir is configured, rejects paths outside that directory.
3. Evaluates the active ToolPermissionPolicy against file_path.

To require user approval before any file write:

permissions:
  mode: default
  ask:
    - "Write"

To restrict writes to a subdirectory:

permissions:
  mode: strict
  allow:
    - "Write(/workspace/**)"

Usage notes

• Prefer Edit for modifying existing files — it sends only the diff.
• Use Write only for creating new files or for complete rewrites.
• Do not create documentation or README files unless explicitly requested.

Example

{ file_path: "/workspace/src/config.ts", contents: "export const PORT = 3000;\n" }

Sandbox variant

The sandboxed Write tool writes into the container filesystem. Paths must be inside /workspace.

Related

• Read
• Edit
• Tool Permissions