Reply To Inbox Message

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

Annotations indicate mutability (readOnlyHint=false), destructiveHint=true, and idempotentHint=true. The description adds the requirement for user approval before sending, which is useful context. However, it does not explain the destructive nature (what gets destroyed) or any side effects beyond sending a reply.

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 description is two sentences, no filler, front-loaded with the core purpose. Every sentence adds value.

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 having an output schema, the description does not explain the return value or how to construct a proper reply (e.g., threading headers, body fields). For a tool with 12 parameters and many nested objects, the description is insufficient for an agent to use it correctly without additional context.

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 only 25% (3 of 12 parameters have descriptions). The description does not elaborate on any parameter beyond referencing the IDs. Many parameters (e.g., cc, html, text, headers) are complex and require explanation, but none is provided.

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 the action ('Reply') and the resource ('JMAP inbox message within its mailbox'), and instructs to use IDs from shipmail_list_mailbox_inbox_messages, which distinguishes it from sibling tools like shipmail_reply_to_inbox_thread or shipmail_send_message.

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?

It provides explicit guidance on when to use (after getting mailbox and message IDs from the list tool) and a constraint (only after user approves recipients and content). It does not list when not to use or mention alternatives, but the reply context makes the usage clear.

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