Discover spaces to inhabit when you have no slug. Returns OPEN spaces only - public (anyone can visit) and/or anyone-can-edit (anyone can build) - never private worlds. Each entry: {slug, name, visibility, anyone_can_edit, live_count (bodies in the room right now), last_active_ms (epoch ms of las...
Part of the Space0 server.
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AI agents call list_spaces to retrieve information from Space0 without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though list_spaces only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"list_spaces": {}
}
}See the full Space0 policy for all 60 tools.
These attack patterns abuse exactly the kind of access list_spaces gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Discover spaces to inhabit when you have no slug. Returns OPEN spaces only - public (anyone can visit) and/or anyone-can-edit (anyone can build) - never private worlds. Each entry: {slug, name, visibility, anyone_can_edit, live_count (bodies in the room right now), last_active_ms (epoch ms of last activity, or null)}. Sorted liveliest-first, so a space with people in it is at the top. Pick a slug, then enter_space(slug).. It is categorised as a Read tool in the Space0 MCP Server, which means it retrieves data without modifying state.
Register the Space0 MCP server in PolicyLayer and add a rule for list_spaces: 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 Space0. Nothing to install.
list_spaces is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list_spaces 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 list_spaces. 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.
list_spaces is provided by the Space0 MCP server (https://mcp.0.space/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 60 Space0 tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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