Ads Update Responsive Search Ad

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

Annotations already signal this is a mutating operation (readOnlyHint=false), but the description adds the non-obvious side effect that 'Editing an ad resets its performance history in the UI.' This is valuable behavioral context beyond what the annotations or schema provide. It does not contradict the annotations.

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?

The description is three sentences with no wasted text: the first states the core action, the second explains the critical full-list behavior, and the third gives the key trade-off and alternative. It is compact, front-loaded, and every sentence 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?

For a complex update tool with 9 parameters, 100% schema coverage, an output schema, and useful annotations, this description covers the essential behavioral, usage, and side-effect information. It does not need to repeat schema details, and the combination of description plus structured fields leaves no important gap for an agent to call this tool correctly.

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 100%, so the baseline is 3, but the description enhances parameter understanding by explaining that headlines and descriptions are replaced as whole sets and that the caller must pass the full intended list. The schema says 'Full replacement list, or omit to keep current,' and the description reinforces the practical implication, which is especially important for array-valued parameters.

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: 'Replaces the copy of an existing responsive search ad.' It clearly identifies the operation as an update to an existing ad rather than a creation, and the additional sentence about A/B tests distinguishes it from ads_create_responsive_search_ad. This is unambiguous and differentiates the tool from its closest sibling.

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 explicitly tells the agent when to use this tool (to replace copy on an existing ad) and when not to: 'for A/B tests prefer creating a second ad in the same ad group.' It also gives a critical usage instruction that replacement sets must be passed whole. This is direct, actionable guidance that prevents common misuse.

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