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

Adds genuinely non-obvious behavior beyond the annotations: the ad re-enters Google review after editing, and the edit will not trigger a spend review so it applies directly. These are real operational consequences the agent could not infer from readOnlyHint=false / destructiveHint=true / openWorldHint=true. It does not state what happens to fields that are omitted from the call.

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 short sentences, front-loaded with the action and resource, followed by the two consequences that matter. No filler and nothing buried.

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?

A mutation tool with 8 parameters, 50% coverage, no output schema and destructive annotation needs more than this: the partial-versus-total replacement rule when only some fields are supplied, the ad_id/account handling, and the dry_run behavior are all unaddressed. The review-cycle note is valuable but does not close those gaps.

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 50%, so the description partially compensates by naming which fields get replaced and confirming the replacement is wholesale ('Replace the headlines' matches the schema's 'Replaces all headlines'). It says nothing about ad_id, account, dry_run, or the path1/path2 display-path constraints, so half the parameters remain unexplained in both places.

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') plus the exact resource ('an existing responsive search ad') and enumerates the mutable fields (headlines, descriptions, final URL, display paths). This clearly separates it from google_ads_create_ad and google_ads_update_display_ad / google_ads_update_app_ad by ad type, though no sibling is named explicitly.

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 word 'existing' plus 'Replace' implies this is the edit path for an already-live RSA, but the description never says when to choose it over google_ads_add_assets, google_ads_add_more_assets, or a full re-create. No exclusions or prerequisites (permissions, ad status) are given.

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