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

No annotations are provided, so the description carries the full burden. It does disclose the content scope returned (full body plus attachment metadata), which implies a safe read, but it omits any side effects (e.g. whether reading marks the message read), error behavior for invalid ids/indices, and any permission requirements.

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 sentence that front-loads the verb and target, then attaches the lookup modes and return scope as parenthetical detail. Nothing is wasted.

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 two simple parameters, no annotations, and no output schema, the description covers purpose and return content (body and attachment metadata), which is what an agent most needs. It stops short of side-effect and failure-mode information, a minor gap for a read 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 description coverage is 100%, and both parameters are documented as coming from list_messages results. The description restates the same origin (id or list index) without adding syntax, precedence, or behavior details beyond the schema, so the baseline 3 applies.

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 (read) and resource (one Nova Inbox message) with the two lookup modes (id or list index) and the return scope (full body, attachment metadata). 'One ... message' implicitly distinguishes it from list_messages and list_thread, but no sibling is named 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?

Usage is only implied: you read a single message, presumably after list_messages produces an index or id. There is no explicit when-to-use, when-not, or named alternative such as list_messages for bulk retrieval.

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