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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety profile is covered. The description adds value by noting the returned chat id is a prerequisite for other tools, but doesn't disclose behavior like ordering, whether conversations are deduplicated, or whether the limit applies to all services equally.

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, zero wasted words. States what it does, what it returns, and how to use it downstream. Front-loaded with the core action and immediately useful context.

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 annotations covering the read-only safety profile, the output schema describing the return structure, and a single self-documenting parameter, the main gap is lack of behavioral detail (ordering, service coverage). Overall quite complete for an entry-point list tool.

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% for the single 'limit' parameter, which has a default documented in the schema. The description doesn't need to add param detail since the schema already covers it. Minor credit for the default 30 being explicit in schema.

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?

Specific verb+resource: lists recent iMessage/Messages.app conversations. Clear scope (chat id, name, service) and distinguishes from siblings by naming what Fields are returned. Establishes this as the entry point for the Messages tool family.

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 states 'Start here for Messages' and names the dependent tools (read_messages/search_messages/send_message) that need the chat id. Gives clear when-to-use guidance that differentiates it from signal_list_chats and teams_list_chats siblings.

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