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

Annotations already declare this as a safe read-only, idempotent operation. The description adds useful behavior beyond annotations: plaintext with no HTML, workspace rejection, and a PHI handling warning. It does not describe not-found or other error behavior.

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?

Four short sentences, each carrying a distinct operational fact. The most important details, return format and messageId prerequisite, are front-loaded with no waste.

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 simple read-only get tool with no output schema, the description covers return format, prerequisite, ownership enforcement, and PHI sensitivity. It is nearly complete, though error handling for missing or inaccessible messages is not detailed beyond workspace rejection.

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 both parameters are already documented. The description adds provenance for messageId, but lovedOneId is only indirectly covered by the workspace rejection note and the schema already calls it an ownership check.

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?

States a specific verb and resource: returns one Family Inbox message. The singular scope and the requirement to get messageId from list_inbox_messages clearly distinguish it from the sibling list tool.

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?

Explains that messageId must come from list_inbox_messages and that workspace ownership is enforced. It gives clear context for use but does not explicitly state when not to use it versus list_inbox_messages or reply_to_inbox_message.

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