mac-messages-mcp

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tool_check_imessage_availability

Check whether a phone number or email is reachable via iMessage. Returns a plain-text status indicating iMessage availability or SMS/RCS fallback, without sending any message.

Instructions

Check whether a recipient appears reachable through iMessage.

This is a read-only availability check against local Messages services; it
does not send a message. Requires Messages to be configured on this Mac.
Returns a plain-text result indicating iMessage availability or likely SMS/RCS
fallback for phone numbers. Use this before tool_send_message when delivery
route matters; use tool_find_contact first if you only have a contact name.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`recipient`	Yes	Phone number or email address to check for iMessage capability.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv1.1.0Sep 7, 2026

addedInput schema / properties / recipient / description

Added value: +"Phone number or email address to check for iMessage capability."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "result": {
+      "title": "Result",
+      "type": "string"
+    }
+  },
+  "required": [
+    "result"
+  ],
+  "title": "tool_check_imessage_availabilityOutput",
+  "type": "object"
+}

First observedAug 19, 2025

TDQS

A5/5.0

Behavior5/5

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

No annotations are provided, but the description clearly states it is a read-only check, does not send a message, and requires Messages to be configured. This fully discloses side effects and prerequisites.

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 concise, uses a clear structure with separate sentences for functionality, constraints, and usage guidance. No unnecessary words or redundant information.

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

Completeness5/5

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

Given the simple tool and known sibling context, the description fully covers what the tool does, its prerequisites, and its output type. It mentions 'plain-text result' and the possible outcomes (iMessage availability or SMS/RCS fallback), which is sufficient.

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

Parameters5/5

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

The recipient parameter description ('Phone number or email address to check for iMessage capability') adds meaningful detail beyond the type, specifying acceptable input formats and purpose. Schema coverage is 100% and description enhances it.

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

Purpose5/5

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

States a specific verb ('check'), resource ('recipient appears reachable through iMessage'), and distinguishes from siblings by mentioning 'use this before tool_send_message' and 'use tool_find_contact first'.

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

Usage Guidelines5/5

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

Explicitly states when to use (before sending, when delivery route matters) and when to use an alternative (if only contact name, use tool_find_contact). Also notes it is read-only and requires Messages configuration.

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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