AI agents call get_canvas 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.
The tool retrieves existing canvas file contents from an Obsidian vault without creating, modifying, or deleting data. This is a straightforward read operation with minimal security risk, as it only exposes information already present in the vault. The blast radius is limited to potential information disclosure about canvas structure and linked nodes.
From the tool's definition Tool name 'get_canvas' and description 'Get canvas file contents' indicate a retrieval operation with no modification or side effects.
Documented attack patterns abuse exactly the kind of access get_canvas 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 get_canvas:
{
"version": "1",
"default": "deny",
"tools": {
"get_canvas": {}
}
}get_canvas is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get canvas file contents. 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 get_canvas: 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.
get_canvas 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 get_canvas 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 get_canvas. 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.
get_canvas is provided by the Obsidian MCP Server MCP server (bazylhorsey/obsidian-mcp-server). 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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29 Obsidian MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.