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

With no annotations, the description carries the full burden. It explicitly discloses that the operation replaces existing cell contents 'without warning' and warns to read first if data matters—important destructive behavior. It also explains how `valueInput` affects interpretation of values (as if typed vs RAW). It does not cover auth requirements or rate limits, but for a destructive write the core behavior is well disclosed. This is strong but not exhaustive, so 4.

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?

Three sentences, each earning its place: the action, the destructive consequence warning, and the value interpretation rule. The most critical information (overwrite) is front-loaded. No filler or repetition.

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 destructive mutation with no annotations and no output schema, the description is incomplete. It omits the range address format, spreadsheet identification, values shape/sizing, and what happens if the range extends beyond data. The warning to read first is useful, but an agent still lacks enough to construct a correct call without guessing. The minimal viable information for safe invocation is not fully present.

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 only 20% (only `mailbox` has a description), so the description must compensate. It does explain `valueInput` semantics ('interpreted as if typed unless valueInput is RAW') and implies `values` are cell content. However, it doesn't explain the expected format for `range` (e.g., A1 notation or sheet name) or `spreadsheetId`, nor the dimensionality requirements of `values`. This leaves four of five parameters under-documented, but the one key ambiguity (`valueInput`) is addressed. Baseline is low coverage, so a 3 reflects partial compensation.

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?

The description opens with a specific verb and resource: 'Overwrite the cells in a range.' This clearly distinguishes the tool from sibling `append_google_sheet_rows` (append vs overwrite) and `clear_google_sheet_range` (clear vs write). The title 'Write cells to a range' reinforces the action. No ambiguity about what the tool does.

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 description gives clear context about destructive behavior and advises reading the range first if data must be preserved, which suggests a prerequisite use of `read_google_sheet_range`. However, it never explicitly says when to use this tool instead of `append_google_sheet_rows` or `clear_google_sheet_range`, nor does it mention any exclusions. Usage guidance is implied through the verb 'overwrite' but not stated as a decision rule.

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