Memory for Mastra agents

• Which value is current. Harny memory is dated: a changed value with a newer timestamp becomes the current value, and the earlier value stays answerable by date.
• When a fact happened. Send a timestamp (ISO 8601 with zone) with each memory so Harny knows when it happened.
• One person across sources. Harny keeps a private memory for each person, and connected sources are read for that person only.

This page uses the Harny MCP server. The key in the header belongs to one person (fsk_), so every call the agent makes is scoped to that person.

A user key (fsk_) names its own user and needs no X-Harny-User header.

import { Agent } from "@mastra/core/agent";
import { MCPClient } from "@mastra/mcp";

export async function accountAssistant(userId: string, userKey: string) {
  const mcp = new MCPClient({
    id: `harny-${userId}`,
    servers: {
      harny: {
        url: new URL("https://api.harny.ai/v1/mcp/mcp"),
        // the signed-in person's key, set by your application
        requestInit: { headers: { Authorization: `Bearer ${userKey}` } },
      },
    },
  });
  return new Agent({
    name: "account-assistant",
    instructions: "Call assemble_context before you answer a question about a customer.",
    model, // the model you already use in Mastra
    tools: await mcp.getTools(),
  });
}

With a person's key (starts with fsk_), the server offers the memory tools. Calls are scoped to the key's user.

• assemble_context is the Recall Memory tool. It returns ranked context from the person's memory and their connected sources, scoped to that person.
• ingest_text is the Ingest Memory tool. It writes text into that person's memory.
• describe is available with any key.

• Use Mastra's own state for the agent's working data during a run, such as the steps of a workflow and the tools it has called.
• Add Harny when the agent needs a person's memory across sessions, with dates on each fact and a way to recall what was true at a given time.