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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description is consistent with that. It adds the iMessage scope and identifier options but does not disclose ordering, pagination, or default limit (which is covered in the schema).

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 a single, concise sentence that front-loads the action and resource, with no wasted words.

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?

For a read-only tool with an output schema and full schema parameter coverage, the description covers the essential identifier options. It could potentially note the mutually exclusive nature of chat_id and contact_name, but the schema already does that, so the description is complete enough.

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 fully documents all three parameters. The description merely restates the chat_id/contact_name parameters without adding new information about limit or constraints.

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 uses the specific verb 'Reads' and clearly identifies the resource as 'messages from an iMessage conversation'. It also distinguishes the tool from siblings like send_message or search_messages by mentioning the two identification methods (chat ID or contact name).

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 implies usage for reading iMessage conversations but does not explicitly state when to prefer it over search_messages or how it complements list_message_chats. No exclusions or alternative tools are mentioned, though the schema hints at list_message_chats for obtaining chat_id.

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