m365_mail_reply

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

Annotations already declare non-readOnly, non-idempotent and non-destructive, but the description adds genuinely new behavior: the call sends immediately (no draft), returns success only with no new message ID, and repeated calls can produce duplicate replies. That duplicate-send and retry guidance is exactly the kind of side-effect disclosure 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?

Three dense sentences, front-loaded with the action, then the sibling disambiguation, then the return/retry caveat. No sentence is filler and each adds a distinct fact.

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 compensates by stating exactly what the response contains ('success only, not a draft or new message ID'). Combined with the duplicate-send warning and messageId sourcing hint, nothing an agent needs to invoke this safely is missing.

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 all three parameters are documented in the schema. The description only slightly enriches replyAll by clarifying that the extra recipients are the original message's, which is close to what the schema already says; baseline 3 applies.

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 ('Send a reply to an existing email immediately') and immediately clarifies the replyAll variant. It explicitly distinguishes itself from the m365_mail_send sibling, so an agent can route correctly without opening either 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 alternative tool and the condition that selects it ('Use m365_mail_send for a new conversation'), and adds a retry rule ('check Sent Items before retrying an uncertain send'). Both the when-to-use and the when-not-to-use are explicit.

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