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

Annotations only carry destructiveHint=true, and the description goes well beyond it: immediate delivery, no recall, no attachment support, a 30-messages-per-minute rate limit, and the default delivery channel. The irreversibility statement directly and consistently reinforces the destructive hint, which is exactly the behavioral context an agent needs before sending.

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?

One dense but well-ordered sentence leads with the irreversible effect, then delivery methods, limitations, rate limits and endpoint. Every clause carries information an agent would otherwise have to guess at.

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 three-parameter mutation with no output schema, the description covers the safety-relevant behavior (irreversibility, rate limit, attachment restriction) and how delivery is chosen. It stops short of saying what happens on failure or what the response contains, but nothing critical to correct invocation is missing.

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%, so all three parameters are already documented, including the email default for communicationType. The description mainly restates delivery options and adds only a small clarification ('booking channel'), so the schema does the bulk of the work and baseline 3 applies.

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 to the guest in a conversation' — which is distinguishable from the read-oriented sibling hostaway_list_conversation_messages without opening either schema. It also names the exact Hostaway endpoint, removing any ambiguity about which operation is being invoked.

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 implies when this tool applies (you have a conversationId and want to reach the guest) and explains delivery channel options, but it never states when NOT to use it or names an alternative tool. A user wanting to read prior messages has to infer that from context rather than being routed to the sibling list tool.

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