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

Clearly discloses that it sends real email, cannot be recalled, passes original content including attachments, and shares a common account. This adds significant behavioral context that annotations (destructiveHint and openWorldHint) only imply, going beyond them.

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 with no fluff, front-loaded with the core function and the critical warning about real email. Every word earns its place, making it easy to skim.

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?

Despite 13 parameters, the schema fully documents each, and the description covers usage context, safety warnings, and alternatives. The output schema exists to clarify return values, so nothing essential is missing for an agent to call it correctly.

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 the schema documents all parameters (to, cc, subject, etc.) with descriptions. The tool description adds minimal parameter-specific detail but emphasizes the 'to' and 'message_id' required fields indirectly. Baseline 3 is appropriate.

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 clearly states 'Forwards one message to new recipients and returns message_id and thread_id' using a specific verb (forward) and resource (message), and implicitly distinguishes from reply tools. It effectively communicates the action and its scope.

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?

Explicitly instructs to check content with `get_agentmail_inbox_message` before forwarding and directs to `post_agentmail_inbox_message_reply` for answering instead, providing clear when-to-use guidance and alternatives.

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