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

Annotations already flag destructiveHint=true, idempotentHint=false, and openWorldHint=true, but the description adds substantive behavior the annotations cannot convey: the send is conditional on no one answering first, it consumes the reply allowance, and the delay is bounded to 1 minute–30 days. It does not explain whether a scheduled reply can be cancelled or what happens if the window passes without the condition being met.

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?

Two sentences, no filler, with the core action and its time window up front and the conditional-send caveat immediately after. Every clause carries information.

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 destructive, non-idempotent write with a referenced confirmation flag (same_reply_to_many_confirmed) and no output schema, the description covers the main risks: delayed execution, conditional delivery, and quota consumption. The gaps are secondary — no guidance on cancellation or on what invalid/past timestamps do.

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 already 100%, so the baseline is 3, but the description contributes a real constraint the schema lacks: the allowed horizon for `when` (1 minute to 30 days). It also reinforces the single-message scope of message_id rather than a list.

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?

The description names a specific verb and resource ('Queues a reply'), scopes it to 'one inbox message' and a bounded future window, which separates it in practice from send_reply and schedule_post. It stops short of naming those siblings explicitly, so the differentiation is inferred from scope rather than stated.

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 only implied: an agent can infer this is the 'reply later' option versus send_reply for immediate sends, but the description never states when to prefer it or when not to. There is no mention of the draft/approval flow siblings (list_reply_drafts, approve_reply_draft) that an agent might otherwise confuse with this tool.

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