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

Annotations already declare readOnly, idempotent, non-destructive, open-world access, so the safety profile is covered. The description adds only that attachment *metadata* (not the file) comes back, and says nothing about permission requirements or not-found behavior for an open-world employer-data read.

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?

A single front-loaded sentence with no waste, but the terseness is under-specification rather than efficiency; nothing about the identifier or the read context is stated.

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?

An output schema exists, so return values needn't be explained, but a one-parameter fetch tool with 0% schema coverage still needs the identifier's origin and the relationship to get_attachment/list_messages. Neither is provided.

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 0% and the sole parameter `id` (a 64-hex-char string) is not explained in the description at all — an agent cannot tell whether it is a message id, an encoded key, or how it relates to the ids returned by list_messages. The description fails to compensate for the coverage gap.

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+resource ("Read an employer message") and adds a scoping detail (attachment metadata included). It is distinguishable from list_messages by the singular 'message' read, but it never names a sibling or states the contrast explicitly.

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?

No when-to-use guidance, no prerequisites, and no mention of alternatives such as list_messages for enumeration or get_attachment for downloading the actual file. The agent must infer the retrieval pattern entirely.

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