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

Annotations already declare the non-read-only, non-destructive, closed-world profile, so the description goes further by disclosing the value-coercion behavior: numbers and dates parse and a leading '=' becomes a live formula. That is genuine behavioral context beyond structured data, though the response shape (rows appended, range written) is not mentioned.

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 with zero filler; the core append semantics come first and the value-interpretation caveat follows. Every clause carries actionable information.

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 5-parameter mutation tool with no output schema, the definition covers placement, value interpretation, and the RAW escape hatch, and the mailbox parameter routes to list_authorized_mailboxes. Only the result payload and the fact that pre-existing rows are untouched are left implicit.

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 60% and the valueInput enum has no schema description, but the description compensates by explaining that values are parsed as if typed and that RAW stores text exactly as given — meaningful semantics the schema omits. The undocumented spreadsheetId is largely self-evident, and mailbox/range are covered in 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?

States a specific verb and resource with positional semantics ('add rows after the last row that holds data'), which cleanly separates it from the overwriting update_google_sheet_range sibling. It never names the alternative tool outright, so an agent must infer the append-vs-update distinction.

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 usual way to add records to a tracker' implies the intended use case, and the value-input guidance hints at the RAW alternative. However, no sibling tool is named and no explicit when-not-to-use condition (e.g., use update_google_sheet_range to modify existing cells) is given.

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