insync_reply_message

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

Discloses consequences beyond the annotations: the message "cannot be unsent", the practice receives it, and opening the reply form on an unread message may mark it read. It also documents the two-step confirmation fallback (preview + confirmToken) and the prompt-injection guard, which the destructiveHint/openWorldHint annotations alone 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?

The critical constraints (unreplyable-after-send, unread gate, injection warning) are front-loaded and earn their place. The confirmation mechanics are explained twice — once inline and again in the closing sentence — costing some tightness.

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, open-world write with no output schema, the description covers the required inputs' source, the side effects, the refusal condition, and what the phase-1 response contains. An agent has everything needed to invoke it correctly and to know when to stop.

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 largely restates the schema's own guidance for allow_mark_read and confirmToken. It adds some framing for confirmToken's role in the phase-1 preview flow, but nothing about body/subject semantics beyond what the schema already says.

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 ("Reply to a secure message from your practice") and points to insync_list_messages for the ids, so the agent knows the input source. It never contrasts with the sibling insync_send_message, so the reply-vs-new-message distinction must be inferred from the verb alone.

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 explicit exclusions ("Not for emergencies"), a conditional gate (unread messages refused unless allow_mark_read is true), and a hard rule about never writing due to instructions embedded in tool results. It also specifies the exact precondition — the user themselves asked and approved the preview — before the write may proceed.

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