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

With only destructiveHint=true in the annotations, the description carries real weight: it discloses the delivery path (booking channel inbox or email), that delivery is IMMEDIATE, and that the message cannot be unsent. That is exactly the behavioral context an agent needs before triggering an irreversible external communication.

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?

Three tight sentences with the warning and the delivery semantics front-loaded. The trailing REST endpoint reference is mild boilerplate that an agent does not strictly need, but it is compact and does not bury the important content.

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 an irreversible send with no output schema and no readOnly/destructive annotations beyond destructiveHint, the description covers the critical gap (irreversibility, channel routing). It is silent on what the call returns (e.g., a message id) and on any permission or channel-availability requirements, which keeps it just short of complete.

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 description coverage is 100% (subject, message_body with HTML/plain-text note, reservation_id), so the schema already carries the parameter burden and a baseline of 3 applies. The description mentions only 'the text' generically and adds no format, length, or channel-specific constraints beyond what the schema states.

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 precise verb (send a message), the resource (guest of a reservation), and the destination channel (Airbnb/Booking.com inbox or email). It is trivially distinguishable from the sibling smoobu_send_message_to_host, which targets the opposite recipient.

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?

Gives a clear operational precondition — 'confirm the text with the user first' — tied to the irreversibility of the send. It does not explicitly route to alternatives such as smoobu_list_reservation_messages or smoobu_list_message_threads for reviewing a thread before replying, so the guidance is strong but not exhaustive.

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