mm_send_peer_message

Send an advisory message to a peer MM session on this machine — the host delivers it as a clearly delimited, guarded turn (never as if it were the receiver’s user). Works across harnesses (a Claude session can message a Codex session and vice versa). Delivery is near-real-time, not instant: the desktop app must be running with the receiving session’s project open. Returns ‘queued’, never ‘delivered’ — this tool cannot observe the receiver reading it.

At a Glance

• Category: Core
• Source: Built-in
• Availability: Listed by default
• Required parameters: 4
• Total parameters: 5

Parameters

Parameter	Type	Required	Description
project_path	string	Yes	Absolute path to the RECEIVING session’s project root (the directory containing .mm/) — the mailbox lives under that project’s .mm/, not the sender’s.
from_session_id	string	Yes	This (the sending) session’s MM session id.
from_label	string	No	A human-readable label for the sender (agent name/model), shown to the receiver alongside the session id.
to_session_id	string	Yes	The receiving session’s MM session id.
message	string	Yes	The message body. Delivered to the receiver as clearly delimited, guarded advisory context.

Example

{
  "tool": "mm_send_peer_message",
  "arguments": {
    "project_path": "/Users/you/projects/my-app",
    "from_session_id": "my-example",
    "from_label": "2026-01-15",
    "to_session_id": "my-example",
    "message": "example-message"
  }
}

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