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

Annotations are sparse, but the description discloses the traits that matter: it sends nothing, the draft expires in 30 minutes, changed/expired content requires a new requestId, and the return payload includes requestId and reviewHash. It also states the default privacy posture ('never private memories/transcripts by default'), which annotations cannot carry.

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?

Purpose and the RSVP exclusion are front-loaded, and each sentence carries distinct information (params, privacy, returns, workflow, expiry). The middle parameter list reads as a schema dump and the chat-workflow sentence is dense, but there is no filler.

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?

With no output schema, the description enumerates the returned fields, and it covers the mutation semantics, expiry/replay rule, and the required next-tool hand-off. An agent has everything needed to invoke it correctly without follow-up questions.

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 0%, so the description carries the burden, and it only partially does: it names all five params and repeats the topic enum (already in the schema) and adds qualifiers ('stable requestId', 'explicit replyEmail'). It says nothing about message length bounds, the eventId/requestId patterns, or why replyEmail must be explicit, leaving real gaps.

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?

Specific verb+resource ('Prepare ONE private message to an event host') with an explicit disambiguation from rsvp_to_event ('not an event RSVP'). The agent can tell it apart from send_host_contact and get_host_contact without opening any schema.

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?

Names the downstream action explicitly ('immediately stage send_host_contact alone with these returned values') and negates the wrong behavior ('Do not ask a separate informal confirmation first'). When-to-use, when-not, and the alternative are all stated rather than inferred.

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