Forward a received message

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

Annotations already cover the safety profile (openWorld, non-idempotent, non-destructive). The description adds real behavioral value beyond them: the same allow list and review/send limit as send_message, the structure of the forwarded payload (note, original header/text, attachments), and the return shape.

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 sentences, front-loaded with the core action and followed by the alternative and constraints. Each sentence earns its place, though the parenthetical detail on attachments could be trimmed.

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 carries the return value ({ message_id, warnings }) and covers the key behavioral constraints. Complete enough for an agent to call it, though it omits details like attachment size or recipient limits.

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 documents all six parameters. The description restates the include_attachments default behavior and the body_markdown placement but adds little the schema doesn't already say, 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 ('Forward a received message to other allowed recipients') and names the sibling it is not (reply_message). An agent can distinguish this from send_message and reply_message 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 explicitly ('Use reply_message to answer the sender instead') and gives context via the send_message constraints. It provides clear routing but stops short of spelling out full when/when-not conditions such as required permissions.

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