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

Annotations declare destructiveHint=true and idempotentHint=false, and the description goes well beyond them: it discloses that nothing is sent, that the original is closed as redirected, the refusal conditions (loop, repeat, opted-out or bounced address), and a referral-chain depth cap of three. That is exactly the operational 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?

Front-loads the surprising fact ('Sends nothing') before the workflow, and every following sentence carries distinct information (new thread, close original, reply routing, refusal rules). Four sentences is slightly dense but there is no filler.

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 mutation with no output schema, the description covers the side effects (thread opened, original closed), reply-routing behavior, and all documented failure/refusal modes. Nothing an agent needs before calling it appears to be 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 description coverage is 100%, so the schema already explains all three parameters with their roles (name optional, email = named address, conversationId from list_inbox/get_thread). The description reinforces the referral semantics but adds no syntax, format, or constraint detail beyond the schema, so the 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 – opens a NEW thread to the referred address, carries the referral, and closes the original as redirected. It also explicitly distinguishes itself from send_reply and draft_reply, so an agent can tell what it does and does not do 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?

Gives an explicit trigger condition ('when somebody replies I am not the right person, talk to X') and an explicit routing exclusion ('it does not change where replies on the old thread go: send_reply still answers the person who referred you'). When-to-use and when-not-to-use are both covered.

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