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

Annotations only say non-read-only, idempotent, non-destructive. The description adds genuinely new behavior: changesets are reversible, concurrency is optimistic via per-cell expectedVersion, cleared cells must carry null with their version, and retries have an idempotency/ambiguity caveat. That is substantial disclosure beyond the annotation set.

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?

Purpose and the 500-cell/reversible scope are front-loaded, and every remaining sentence is an actionable rule rather than filler. It is dense and clause-heavy, but nothing is padding.

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 3-param, version-sensitive bulk mutation with an output schema available, the description covers value validation, option-ID vs label, version sourcing, clear semantics, and retry behavior. An agent has what it needs to call this correctly without guessing.

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 only 33%, and the description compensates: it explains expectedVersion semantics (copy from a prior read; "0" only for absent/newly inserted cells), the correct array name to populate, and column-type value rules that the schema only partially states. This meaningfully extends what the schema provides.

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?

State a precise verb+resource+scope: 'Update up to 500 explicit cells as one reversible changeset.' The expectedVersion/cleared-cell language makes it clear this targets existing rows, implicitly separating it from insert-style siblings, but no sibling tool (sheets_insert_records, sheets_add_rows, sheets_update_column) is named for direct routing.

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?

Gives concrete operating context: read the requested cells first, pass each cell's entityVersion as expectedVersion, use "0" only when the cell is absent or newly inserted, and send items in `patches` not `cells`. Strong how-to guidance, though it never states when to prefer this tool over sibling update/insert tools.

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