session_lessons · Heimdall MCP Server MCP: Risk & Policy

WHAT IT DOES

What session_lessons does on Heimdall MCP Server

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

WHY IT NEEDS A POLICY

Why session_lessons needs a policy

The tool writes new lesson/memory entries derived from the current session into persistent storage. It creates or updates data (session learnings) that persists across sessions. It does not delete or execute code, making Write the most appropriate category. Medium severity because an AI agent could store misleading or incorrect learnings that corrupt future context.

From the tool's definition 'Capture and consolidate key learnings from current session for future reference' — stores/writes new memory data persistently

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

session_lessons Rate-limited

session_lessons 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": {
    "session_lessons": {
      "limits": [
        {
          "counter": "session_lessons_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 Heimdall MCP Server, so you can run agents against it safely.

FAQ

Questions about session_lessons

What does the session_lessons tool do? +

Capture and consolidate key learnings from current session for future reference. This tool encourages metacognitive reflection - thinking about what you. It is categorised as a Write tool in the Heimdall 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 session_lessons? +

Register the Heimdall MCP Server MCP server in PolicyLayer and add a rule for session_lessons: 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 Heimdall MCP Server. Nothing to install.

What risk level is session_lessons? +

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

Can I rate-limit session_lessons? +

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

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

session_lessons is provided by the Heimdall MCP Server MCP server (lcbcfoo/heimdall-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.