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

Annotations already declare read-only, idempotent, non-destructive behavior, so the bar is lower; the description still adds real context by warning that PHI may appear in subjects and previews and that HTML bodies are excluded. It does not cover ordering guarantees or pagination beyond what the schema states.

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?

Three compact sentences: what is returned first, then the payload boundary, then the scope/PHI caveats. Every sentence carries distinct information with no repetition of the name or title.

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 no output schema, the description compensates by enumerating returned fields and the PHI exposure, and the single required parameter is schema-documented. Minor gap: ordering of 'recent' messages and paging behavior beyond limit are not described.

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%, with lovedOneId pointing to list_loved_ones and limit bounded 1-50 default 20, so the schema carries parameter meaning. The description reinforces that exactly one loved one is in scope but adds no syntax or format detail beyond the 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 (Lists) + resource (messages in one loved one's Family Inbox) + explicit field set returned (subject, sender, category, preview). It is clearly distinguished from the singular sibling get_inbox_message by being a list over one loved one's inbox.

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 scope constraint ('caller's family workspace only') and the note that HTML bodies are not returned implicitly steer the agent to get_inbox_message for full content, but no sibling is named and there is no explicit when-to-use/when-not statement. Usage is inferable rather than stated.

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