write_page · Silverbullet MCP: Risk & Policy

WHAT IT DOES

What write_page does on Silverbullet

AI agents use write_page to create or update resources in Silverbullet — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Silverbullet environment.

WHY IT NEEDS A POLICY

Why write_page needs a policy

This tool creates or modifies data reversibly. Although 'OVERWRITES' suggests replacement, the collision-safety mechanism and ability to re-read/re-write the page means the action is not irreversible like a destructive delete. The primary risk is unintended modification of note content, which is significant but containable through reading the prior state.

From the tool's definition Tool name is 'write_page' and description states it 'OVERWRITES an existing page wholesale', which modifies data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

write_page Rate-limited

write_page 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Silverbullet, so you can run agents against it safely.

FAQ

Questions about write_page

What does the write_page tool do? +

OVERWRITES an existing page wholesale. Requires expected_last_modified — the lastModified value the caller obtained from a prior read_page (or list_pages). If the server. It is categorised as a Write tool in the Silverbullet MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on write_page? +

Register the Silverbullet MCP server in PolicyLayer and add a rule for write_page: 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 Silverbullet. Nothing to install.

What risk level is write_page? +

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

Can I rate-limit write_page? +

Yes. Add a rate_limit block to the write_page 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 write_page completely? +

Set action: deny in the PolicyLayer policy for write_page. 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 write_page? +

write_page is provided by the Silverbullet MCP server (xmatthewx/silverbullet-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.