add_card_to_canvas

THE RISK

Medium Risk

Why add_card_to_canvas needs a policy

This tool creates new card objects on an Obsidian canvas, which is a reversible modification of canvas data. It does not execute arbitrary code, delete data irreversibly, or move money. The severity is medium because misuse could add unwanted clutter or misleading information to a user's canvas, but the effect is recoverable by deleting the added card.

From the tool's definition Tool description states 'Add text/note/media card to canvas' — this creates new content (a card) on a canvas, modifying the canvas structure. The verb 'Add' and the action of creating a new card element constitute data creation.

Documented attack patterns abuse exactly the kind of access add_card_to_canvas gives an agent:

POLICY

How to control add_card_to_canvas

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_card_to_canvas:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "add_card_to_canvas": {
      "limits": [
        {
          "counter": "add_card_to_canvas_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

add_card_to_canvas 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.

Create a free account and register Obsidian MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about add_card_to_canvas

What does the add_card_to_canvas tool do? +

Add text/note/media card to 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.

How do I enforce a policy on add_card_to_canvas? +

Register the Obsidian MCP Server MCP server in PolicyLayer and add a rule for add_card_to_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.

What risk level is add_card_to_canvas? +

add_card_to_canvas is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit add_card_to_canvas? +

Yes. Add a rate_limit block to the add_card_to_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.

How do I block add_card_to_canvas completely? +

Set action: deny in the PolicyLayer policy for add_card_to_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.

What MCP server provides add_card_to_canvas? +

add_card_to_canvas 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.

Enforce policy on every Obsidian MCP Server tool call.

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.

CHECK YOUR STACK →