agent-mailbox

mailbox_send

Send messages to individual agents, multiple agents, or broadcast to all. Enables asynchronous inter-agent communication via local mailboxes.

Instructions

Send a message to one agent, a list of agents, or "all" for broadcast.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "to": "<to>",
      "subject": "<subject>",
      "body": "<body>"
    },
    "name": "mailbox_send"
  }
}

Input Schema

Name	Required	Default
`to`	Yes
`body`	Yes
`from_id`	No
`subject`	Yes
`priority`	No	normal
`reply_to`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 5, 2026

TDQS

B3.2/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden of behavioral disclosure. It does reveal a meaningful behavior: the special value all means broadcast. However, it does not explain delivery, side effects, return behavior, or how this differs from the mailbox_broadcast sibling.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is one concise sentence with no wasted words and front-loads the primary action and recipient variants. It is easily scannable and appropriately tserse for what it communicates.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with no annotations, no output schema, and multiple sibling tools, this description is too minimal. It lacks the distinction from mailbox_reply/broadcast, does not describe what happens after sending, and does not cover the optional parameters or their effects.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description adds helpful meaning for the to parameter by explaining one, list, and all as valid target forms. But with zero schema description coverage, it leaves subject, body, from_id, and priority semantically unexplained, so the description only partially compensates.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb and resource: send a message. It clearly lists the recipient forms: one agent, a list of agents, or all. However, it does not differentiate this tool from sibling tools like mailbox_broadcast or mailbox_reply, so it lacks full sibling separation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage: use this tool when you want to send a message to one recipient, several recipients, or to everyone. It gives no explicit when-not-to-use guidance and does not mention alternate tools such as mailbox_reply or mailbox_broadcast.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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