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

Annotations already declare readOnlyHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely non-redundant context: it is a metadata-only read that returns no cell values, which tells the agent it is cheap to call before deciding where to 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?

Two sentences, zero waste, front-loaded with the what and immediately followed by the why/when. Every clause earns its place.

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?

Without an output schema, the description usefully summarizes the return shape (worksheets plus occupied ranges) and its role in the read workflow. Only minor gap is where workbookId comes from, which leaves it slightly short of fully self-sufficient.

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 50%: mailbox is documented (with a pointer to list_authorized_mailboxes) but workbookId has no schema description, and the description adds no format or provenance detail such as obtaining the ID from list_excel_workbooks. Baseline 3 applies since the description does not compensate for the 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 (read), resource (workbook), and precise scope: 'shape without reading cells: its worksheets and, for each, the occupied range.' This cleanly distinguishes it from read_excel_range (reads cells) and list_excel_workbooks (lists workbooks) without needing to open another schema.

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?

'Call this first ... then read from the one you want' gives explicit sequencing and the condition that selects this tool versus the range-reader. It stops short of naming read_excel_range and offers no when-not guidance, but the intended workflow is unambiguous.

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