Threshold

Message the host

send_message

Send a message to the host on the guest's behalf, e.g. a question about check-in or a late arrival. Only send what the guest asked you to say. The host is emailed and replies appear in get_messages. Open from the request until two weeks after check-out.

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": {
      "booking_id": "<booking_id>",
      "body": "<body>"
    },
    "name": "send_message"
  }
}

Input Schema

Name	Required	Description
`body`	Yes	The message to the host, in the guest's words, up to 2,000 characters.
`booking_id`	Yes	The booking the message is about.
`guest_email`	No	The email the booking was made with. Needed unless you connect with an agent token.

Output Schema

Name	Required	Description	Default
`message`	No	The message.

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedOct 14, 2026

addedInput schema / properties / body / description

Added value: +"The message to the host, in the guest's words, up to 2,000 characters."

addedInput schema / properties / booking_id / description
```
Added value: +"The booking the message is about."
```

addedInput schema / properties / guest_email / description

Added value: +"The email the booking was made with. Needed unless you connect with an agent token."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "description": "The message as sent.",
+  "properties": {
+    "message": {
+      "additionalProperties": true,
+      "description": "The message.",
+      "properties": {
+        "body": {
+          "type": "string"
+        },
+        "sent_at": {
+          "type": "string"
+        }
+      },
+      "type": "object"
+    }
+  },
+  "type": "object"
+}

First observedOct 2, 2026

TDQS

A3.7/5.0

Behavior4/5

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

Beyond the annotations (readOnlyHint=false, openWorldHint=true), the description discloses the side effect that the host is emailed and that replies surface via get_messages, plus the lifespan of the channel. That is genuinely useful behavioral context an agent cannot get from the structured fields, though it says nothing about delivery failure or rate limiting.

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

Conciseness4/5

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

Three short sentences, front-loaded with the purpose and ending with the channel's lifetime; each sentence carries distinct information. The window phrasing ('Open from the request until two weeks after check-out') is slightly terse but not wasteful.

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

Completeness4/5

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

With an output schema present, return values need not be explained, and the description still usefully says where replies appear. Combined with annotations covering the safety profile, the only real hole is the unresolved distinction from ask_host.

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

Parameters3/5

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

Schema description coverage is 100%, so booking_id, body and guest_email are already documented in the schema, and the baseline is 3. The description only reinforces the 'in the guest's words' intent for body and adds no syntax, format or conditional requirements beyond the schema.

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?

States a specific verb+resource ('Send a message to the host') and adds concrete examples (check-in question, late arrival), so the agent knows exactly what the tool produces. It does not, however, distinguish itself from the sibling 'ask_host', whose name implies a highly similar action, and that overlap is left unresolved.

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?

It gives a content constraint ('Only send what the guest asked you to say') and an availability window ('Open from the request until two weeks after check-out'), which are real usage conditions. But it never states when to pick this over ask_host or how to handle a guest who wants something broader, so routing between the two messaging siblings is left to inference.

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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