AI agents use add_canvas_edge to create or update resources in Obsidian MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Obsidian MCP Server environment.
This tool creates new relationships/connections in a canvas, which is a reversible modification of canvas metadata. It does not execute arbitrary code, delete data, or trigger external operations. It fits the Write category as it modifies canvas structure non-destructively.
From the tool's definition Tool name 'add_canvas_edge' and description 'Add an edge between nodes in canvas' indicate modification of canvas data structure by creating connections between existing nodes.
Documented attack patterns abuse exactly the kind of access add_canvas_edge 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 add_canvas_edge:
{
"version": "1",
"default": "deny",
"tools": {
"add_canvas_edge": {
"limits": [
{
"counter": "add_canvas_edge_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_canvas_edge 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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Add an edge between nodes in canvas. It is categorised as a Write tool in the Obsidian MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Obsidian MCP Server MCP server in PolicyLayer and add a rule for add_canvas_edge: 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.
add_canvas_edge 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 add_canvas_edge 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 add_canvas_edge. 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.
add_canvas_edge 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.