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

Annotations already declare readOnlyHint=false and destructiveHint=false, so safety is covered; the description adds genuinely new behavioral context by specifying this is a partial merge ('Fields left out keep their values'), which is not derivable from the annotations. It does not mention the confirmation/approval flow implied by approvalId, so it is not exhaustive.

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 tight sentences with no filler; the core action and the id-source pointer are front-loaded. Every clause carries information an agent needs.

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 mutation tool whose annotations already carry the safety profile, the description covers action, targeting, and merge semantics adequately, and the absence of an output schema means return values need not be explained. Minor gaps remain: the schema-only approval flow and the 200-item cap are not echoed, but they are documented in the schema.

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?

With 80% schema coverage the baseline is 3, but the description adds real meaning to the `updates`/`fields` payload by explaining that omitted fields are preserved rather than cleared. Other parameters (sheetId, table, workspace) are handled adequately by 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 (changes), resource (fields of records in a sheet table), and mechanism (by id), which cleanly separates it from siblings like napkin_tables_add_records and napkin_tables_delete_records. It also names napkin_tables_query as the source of ids, giving the agent a clear entry point.

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?

It supplies a concrete prerequisite/cross-tool path by directing the agent to obtain ids from napkin_tables_query, which is clear usage context. It does not spell out when NOT to use this tool (e.g. full-row replacement vs. cell edits), so it falls short of full when/when-not guidance.

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