AI agents call extract_code_blocks 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 reads code blocks from existing notes without creating, modifying, or deleting any data. It is a passive query operation with no ability to alter state or trigger external operations. The blast radius of misuse is minimal—an AI agent could only over-extract or repeatedly query, which poses no meaningful risk.
From the tool's definition Tool name 'extract_code_blocks' and description 'Extract all code blocks from a note' indicate data retrieval with no modifications or side effects.
Documented attack patterns abuse exactly the kind of access extract_code_blocks 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 extract_code_blocks:
{
"version": "1",
"default": "deny",
"tools": {
"extract_code_blocks": {}
}
}extract_code_blocks is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Extract all code blocks from a note. 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 extract_code_blocks: 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.
extract_code_blocks 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 extract_code_blocks 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 extract_code_blocks. 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.
extract_code_blocks 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.
Free to start. No card required.
120 Obsidian MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.