archive_thought · Brain MCP: Risk & Policy

WHAT IT DOES

What archive_thought does on Brain

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

WHY IT NEEDS A POLICY

Why archive_thought needs a policy

This tool modifies data by marking thoughts as archived (soft-delete), which changes their state and excludes them from queries. This is a Write operation because the action is reversible (the tool description indicates data is 'preserved for history' and contrasts with supersede_thought for replacement, implying archive can be undone).

From the tool's definition Archive a thought without replacing it. Use this to remove duplicates, mistakes, or irrelevant thoughts. The thought is soft-deleted (marked archived)...

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

archive_thought Rate-limited

archive_thought 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": {
    "archive_thought": {
      "limits": [
        {
          "counter": "archive_thought_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 Brain, so you can run agents against it safely.

FAQ

Questions about archive_thought

What does the archive_thought tool do? +

Archive a thought without replacing it. Use this to remove duplicates, mistakes, or irrelevant thoughts. The thought is soft-deleted (marked archived) and excluded from normal queries, but preserved for history. To replace a thought with updated content, use supersede_thought instead. It is categorised as a Write tool in the Brain MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on archive_thought? +

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

What risk level is archive_thought? +

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

Can I rate-limit archive_thought? +

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

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

archive_thought is provided by the Brain MCP server (markschaake/brain-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.