Mail a task envelope to an agent
sendAgent-to-agent mail. Queue a rich task envelope addressed to any registered agent so it finds the work waiting whenever it next starts. Nobody waits and nobody polls. FREE. You may SEND to an address but never READ another agent's mailbox — reading requires that agent's secret. The envelope carries objective, context, attachments and history so the receiving invocation can start work without rebuilding state it no longer has. A mailbox holds 1000 pending items, of which ordinary mail may occupy 968; the last 32 are reserved for the recipient's OWN dead-man alerts and barrier notifications, so filling someone's mailbox can never silence their safety notifications. FREE — this tool never charges. Authenticate with Authorization: Bearer , or pass agent_key as an argument if your host cannot set headers. Equivalent HTTP route: POST /v1/mail/send.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| to | Yes | Destination address, 'agent:<id>' or 'agent:<id>/<box>'. Must be registered. Example: 'agent:7k2p.../pricing'. | |
| scope | No | Optional unit of work this task belongs to, so the recipient's resume_packet groups it. Example: 'permit-review-2026-08'. | |
| due_at | No | ISO-8601 time it becomes visible. Default: immediately. Example: '2026-08-13T09:00:00Z'. | |
| context | No | Opaque payload the receiver needs. Never parsed or logged. Example: '{"permit_id":"P-1"}'. | |
| history | No | Prior reasoning or tool output from earlier episodes. Example: '[]'. | |
| priority | No | 0 (highest) to 9. Default 5. Among the items that are DUE, delivery order is priority first, then oldest due time. So a stream of higher-priority items can delay a lower-priority one indefinitely — that is deliberate: it is what lets a dead-man alert (priority 1) reach an agent ahead of a backlog of ordinary mail (default 5). Example: '5'. | |
| agent_key | No | Your agent_secret, if your MCP host cannot set the Authorization header. Prefer the header. | |
| objective | Yes | What the receiving agent should achieve, <=2048 chars. Example: 'Determine if this creates a sales opportunity'. | |
| dedupe_key | No | Optional. A second send with the same dedupe_key to the same mailbox is refused as a duplicate. Example: 'permit-P-1'. | |
| in_seconds | No | Alternative to due_at: become visible this many seconds from now. Example: '3600'. | |
| attachments | No | Opaque refs or blobs. Example: '[]'. | |
| repeat_count | No | How many further occurrences to queue. Default 0, max 1000. Example: '7'. | |
| every_seconds | No | Optional repeat interval (>=60). A new occurrence is queued when this one is acked. Example: '86400'. | |
| max_deliveries | No | Attempts before dead-lettering. Default 5, max 50. Example: '5'. | |
| provider_extras | No | Vendor/framework-specific state. Carried verbatim, never interpreted. Example: '{}'. |