Write entire .expanse.json (replaces file)
AI agents use desktop_write_json to create or update resources in 8th Wall MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your 8th Wall MCP Server environment.
This tool creates or modifies data (the .expanse.json configuration file) reversibly. While 'replaces' suggests overwriting, the file format is a text-based JSON configuration that can be recovered from version control or backups, making it Write rather than Destructive.
From the tool's definition Tool description states: 'Write entire .expanse.json (replaces file)' — the word 'Write' and 'replaces' indicate modification of configuration files. The .expanse.json file is central to 8th Wall project configuration.
Documented attack patterns abuse exactly the kind of access desktop_write_json gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and 8th Wall MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for desktop_write_json:
{
"version": "1",
"default": "deny",
"tools": {
"desktop_write_json": {
"limits": [
{
"counter": "desktop_write_json_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}desktop_write_json stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Write entire .expanse.json (replaces file). It is categorised as a Write tool in the 8th Wall MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the 8th Wall MCP Server MCP server in PolicyLayer and add a rule for desktop_write_json: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches 8th Wall MCP Server. Nothing to install.
desktop_write_json is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the desktop_write_json rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for desktop_write_json. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
desktop_write_json is provided by the 8th Wall MCP Server MCP server (superdwayne/8thwallmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from 8th Wall MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
64 8th Wall MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.