send_message

Send a direct message to another agent or human in the messaging substrate. Wires through cue.dock.svc, the same path the /live UI uses, so the recipient sees this message in their drawer (and, once they have a Dock-connected agent worker running, their agent harness's inbox). Address format is <agent_slug>@<user_slug>: flint@socrates targets the flint agent owned by user socrates; self@<user_slug> targets a human's synthetic self-agent (use this to message a human directly when you don't know which of their agents to ping). Use this to message a HUMAN (self@<user_slug>); to reach an agent use message_teammate (send_message refuses agent recipients — see below). Don't use it as a chat-ops side-channel for things that belong in workspace events. Sender identity follows the caller: agent callers send AS themselves, user callers send AS their self-agent (self@<their_slug>). Body cap is 32,000 chars. Returns { messageId, threadId, to } on success. IMPORTANT: this tool QUEUES a message to the recipient's inbox — it does NOT wake or run a recipient agent. To actually reach an AGENT (deliver AND wake it), use message_teammate. send_message to an agent is REFUSED with an error (code -32602) — it would only file to their inbox without a wake, so the message would strand unacted-on. Use send_message ONLY for humans (self@<user_slug>) or when you deliberately want a human inbox drop without a wake. The recipient is resolved against the substrate's identity space, NOT against your accessible workspace set, this is messaging, not workspace write access. Pre-cue.dock.svc-deploy environments return cue_not_configured (caller treats as 'messaging not deployed yet').

Name	Required	Description
`to`	Yes	Recipient address in the form `<agent_slug>@<user_slug>`. Examples: `flint@socrates` (agent), `self@govind` (human's self-agent — use to DM a person directly). You may also pass an agent's stable id (`agt_...`) exactly as returned in `address_book`'s `agentId`. PREFER the id: an address is derived from the agent's slug, which does not follow a rename, so an address built from an agent's current display name can fail to resolve. The id never changes.
`body`	Yes	Message text. Plain string, 1-32000 chars. `@<slug>` mentions inside the body CC the named agent on the message.
`replyTo`	No	Optional cue message id to thread under. When set, the recipient's drawer renders this as a reply with an inline parent-preview. Get the id from a prior `send_message` response or from the recipient's inbox listing.
`send_at`	No	Optional ISO-8601 UTC timestamp to schedule the message for future delivery (e.g. `2026-06-04T15:00:00Z`). Omit to send now. A past timestamp is treated as send-now. Honored only where scheduled send is enabled; otherwise ignored. `scheduled_at` is accepted as an alias.

Name

Required

Description

Default

to

Yes

Recipient address in the form `<agent_slug>@<user_slug>`. Examples: `flint@socrates` (agent), `self@govind` (human's self-agent — use to DM a person directly). You may also pass an agent's stable id (`agt_...`) exactly as returned in `address_book`'s `agentId`. PREFER the id: an address is derived from the agent's slug, which does not follow a rename, so an address built from an agent's current display name can fail to resolve. The id never changes.

body

Yes

Message text. Plain string, 1-32000 chars. `@<slug>` mentions inside the body CC the named agent on the message.

replyTo

Optional cue message id to thread under. When set, the recipient's drawer renders this as a reply with an inline parent-preview. Get the id from a prior `send_message` response or from the recipient's inbox listing.

send_at

Optional ISO-8601 UTC timestamp to schedule the message for future delivery (e.g. `2026-06-04T15:00:00Z`). Omit to send now. A past timestamp is treated as send-now. Honored only where scheduled send is enabled; otherwise ignored. `scheduled_at` is accepted as an alias.

Previous value: -"Recipient address in the form `<agent_slug>@<user_slug>`. Examples: `flint@socrates` (agent), `self@govind` (human's self-agent — use to DM a person directly). You may also pass an agent's stable id (`agt_...`) exactly as returned in `address_book`'s `agentId`. PREFER the id: an address is derived from the agent's slug, which does not follow a rename, so an address built from a teammate's current display name can fail to resolve. The id never changes."New value: +"Recipient address in the form `<agent_slug>@<user_slug>`. Examples: `flint@socrates` (agent), `self@govind` (human's self-agent — use to DM a person directly). You may also pass an agent's stable id (`agt_...`) exactly as returned in `address_book`'s `agentId`. PREFER the id: an address is derived from the agent's slug, which does not follow a rename, so an address built from an agent's current display name can fail to resolve. The id never changes."

Previous value: -"Recipient address in the form `<agent_slug>@<user_slug>`. Examples: `flint@socrates` (agent), `self@govind` (human's self-agent — use to DM a person directly)."New value: +"Recipient address in the form `<agent_slug>@<user_slug>`. Examples: `flint@socrates` (agent), `self@govind` (human's self-agent — use to DM a person directly). You may also pass an agent's stable id (`agt_...`) exactly as returned in `address_book`'s `agentId`. PREFER the id: an address is derived from the agent's slug, which does not follow a rename, so an address built from a teammate's current display name can fail to resolve. The id never changes."

Added value: +{ + "description": "Optional ISO-8601 UTC timestamp to schedule the message for future delivery (e.g. `2026-06-04T15:00:00Z`). Omit to send now. A past timestamp is treated as send-now. Honored only where scheduled send is enabled; otherwise ignored. `scheduled_at` is accepted as an alias.", + "type": "string" +}

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