list_message_targets

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

Without annotations, the description carries full burden. It explains the tool returns two lists, details key fields (im_status with state definitions and timeouts, channel_type with distinctions, members, unread counts), and notes that conversations are those the sender belongs to and hasn't archived. It does not mention whether the operation is read-only or any authentication needs, but the listing nature is clear.

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 longer than typical but is well-structured: a bold imperative line, followed by a clear explanation of the two lists with bullet points, and ending with usage guidance. Each sentence serves a purpose, though some details (e.g., the idle time for 'away') could be trimmed without losing core meaning.

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?

Given zero parameters, an output schema (present but not shown), and no annotations, the description provides comprehensive context: why the tool exists ('an agent that cannot see the roster invents ids'), what data it returns with field explanations, when to call it (before any send), and how to use the results with sibling tools. The only slight gap is not explicitly stating it's read-only, but that's strongly implied.

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?

The input schema has zero parameters, so there are no parameter semantics to describe. With 0 parameters, baseline is 4. The description focuses on output context but adds value by explaining what the returned data represents, which is helpful even though no parameters exist.

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 explicitly states 'Who can be messaged and where' and breaks down the two lists: users (with presence) and conversations (with type and membership). It clearly distinguishes from sibling messaging tools like send_direct_message and send_channel_message by naming them and contrasting their roles.

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?

The description opens with 'ASK THIS BEFORE SENDING ANYTHING,' establishing when to use it. It provides conditional advice (check presence before messaging) and explicitly directs to send_direct_message for individuals and send_channel_message for conversations, while noting notify_user is for annotating invoices/orders.

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