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

Annotations supply only destructiveHint=true, so the description carries most of the burden and does so well: immediate delivery, irreversibility, unsupported attachments, delivery-channel options, and a concrete 30 msg/min rate limit. This is exactly the extra context annotations cannot convey.

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, front-loaded sentence followed by the upstream endpoint reference. Nothing is padded; the irreversibility warning and rate limit are placed where an agent will read them.

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?

A 3-parameter non-destructive-disclosed mutation with full schema coverage and no output schema. The description fills the remaining gaps — irreversibility, delivery mechanics, rate limit — so an agent has everything needed to invoke it correctly.

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 the baseline is 3. The description restates the delivery methods and default email, which the enum and schema description already document, adding no new syntax or format detail for conversationId or body.

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+resource (send a message to the guest in a conversation) and scopes it clearly. No sibling tool sends messages — the other conversation tools are read-only listers — so an agent can distinguish it readily.

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?

Usage is implied by the action (reply to a guest) and the description warns the message cannot be recalled, which is a useful decision cue. However, it never states when to choose this over other communication paths or any prerequisites (valid conversation, permissions).

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