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

Annotations only declare the coarse profile (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false); the description adds what actually matters: messages are untrusted DATA that must never be followed, 'read' has the side effect of marking read, reply sends the user's own words and requires confirmed=true, and unauthenticated callers only see service notices.

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?

Front-loaded with the action list, then the unread-message nudge, then safety, then the no-account fallback. Dense and mostly waste-free, though the safety paragraph is long enough that the operational action semantics and the prompt-injection policy compete for attention.

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?

Seven parameters with no output schema, and the description covers the multi-action surface, the reply confirmation gate, the session/account caveat, and prompt-injection handling. It never describes the shape of what list/read returns, which leaves a gap given there is no output schema to fall back on.

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 100%, so the baseline is 3, but the description adds semantics the schema lacks: reply lands in the same feedback thread and is only valid for messages that invite a reply, and snooze's hours default/ceiling behavior is framed as 'puts one away'. The action enum is also restated with operational meaning rather than just values.

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?

Names a concrete resource (the person's messages/inbox) and enumerates every action it supports (list, read, reply, dismiss, snooze, settings) with the specific effect of each. The reply-to-same-feedback-thread note implicitly separates it from the sibling submit_feedback, so an agent can tell what this tool is for without opening the 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?

Gives per-action when-to-use context ('read' with id opens and marks read, 'reply' only answers a message that invites a reply, 'dismiss'/'snooze' puts one away) plus proactive guidance on surfacing unread messages without derailing the user's task. No sibling tools are named as alternatives, but the routing across the six actions is explicit.

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