AI agents call list_all_tags to retrieve information from Obsidian MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and lists metadata (tags) from the vault without creating, modifying, deleting, or executing any operations. It is a simple enumeration/query function with no capability to alter state or trigger external actions. The blast radius of misuse is minimal—an AI could only discover what tags exist in the vault.
From the tool's definition Tool name 'list_all_tags' and description 'Get all unique tags used across the vault' indicate a retrieval operation with no side effects. The verb 'Get' and the query nature confirm this is a read-only operation.
Documented attack patterns abuse exactly the kind of access list_all_tags gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Obsidian MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_all_tags:
{
"version": "1",
"default": "deny",
"tools": {
"list_all_tags": {}
}
}list_all_tags is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get all unique tags used across the vault. It is categorised as a Read tool in the Obsidian MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Obsidian MCP Server MCP server in PolicyLayer and add a rule for list_all_tags: 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 Obsidian MCP Server. Nothing to install.
list_all_tags 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_all_tags 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_all_tags. 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_all_tags is provided by the Obsidian MCP Server MCP server (kynlos/obsidian-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Obsidian MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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120 Obsidian MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.