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

Annotations already flag destructiveHint=true. The description adds substantive behavior beyond that: field merge semantics (None = keep), status inheritance from the old ad, optional status override (ENABLED|PAUSED), and pausing instead of deleting via keep_old. It does not contradict 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?

Front-loads the core replacement pattern in the first sentence and then adds necessary constraints. The text is dense but every sentence adds information; there is little waste.

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 replace operation, the description covers the mechanism, constraints, status behavior, and keep_old alternative. An output schema exists so return values need not be described; minor gaps are lack of explicit error or edge-case guidance.

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 0%, so the description must compensate. It clarifies keep_old, allowed status values, workspace optionality, and merge semantics for fields, but does not explain ad_id, ad_group_id, or enumerate all mutable fields like headlines, descriptions, final_urls, path1, path2.

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 'replace' and resource 'ad', and explains the underlying pattern (read, merge, create, remove) because Google Ads has no direct edit. It does not explicitly name the sibling ads_update_ad to differentiate, but the mechanism is clear enough for an agent to distinguish the operation.

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?

Explains when this pattern is necessary (Google Ads disallows direct editing), the key constraint (only Responsive Search Ads), and the keep_old alternative to deletion. It does not explicitly compare with ads_update_ad or ads_create_ad, but the context is clear.

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