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

Annotations only flag destructiveHint=true; the description goes further by explaining *why* it is destructive ('cannot be unsent') and enumerating the delivery channels (Airbnb, Booking.com, Vrbo, email). It still omits auth requirements, rate limits, and failure behavior, so it is strong but not exhaustive.

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

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

Two tight sentences with the default behavior front-loaded and the irreversibility warning attached to the mode it applies to; the trailing endpoint reference is a minor but non-wasteful anchor.

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

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

For a 3-parameter destructive mutation with no output schema, the description covers mode semantics, delivery path, and irreversibility. It does not describe what the call returns (e.g., message identifier), which would be the only remaining gap.

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

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

Schema coverage is already 100%, so the baseline is 3, but the description adds real meaning beyond the schema's terse 'host (to the guest, default) or internalNote (private)' by spelling out channel routing and irreversibility for host mode. bookingId and message get no extra treatment beyond the schema.

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

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

States a specific verb and resource ('Send a message on a booking's conversation') and anchors it with the underlying API route (POST /bookings/messages). It is immediately distinguishable from read-oriented siblings like beds24_list_booking_messages and beds24_mark_messages_read.

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

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

The description explains the two operating modes and their consequences: source=host (default) routes through the guest's channel, while source=internalNote is a private host note. That is genuine when-to-use guidance, though it never names sibling alternatives such as mark_messages_read for handling replies.

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