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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), so the description only needs to add context. It contributes the account-vs-campaign scope choice and the https constraint for images, but says nothing about validation failures, whether existing assets are replaced or appended, or what a successful call returns.

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 short sentences; the capability and target are stated first and the sibling-routing parenthetical is placed last where it does not obstruct the main claim. No filler.

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 six-parameter mutation tool with a nested snippets object and no output schema, the description covers what is added and where, but leaves gaps around append-vs-replace behavior, limits, and result reporting. Adequate to select and call the tool, not complete enough to predict outcomes.

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 50% (account, dry_run, image_urls documented; snippets, campaign_id, business_name bare), so the description partially compensates by naming business name and snippets as inputs and implying campaign_id is optional via 'to a campaign or the account'. It adds no detail on snippet headers/values or asset-count limits beyond what the schema already encodes.

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?

Specific verb (add) plus enumerated resources (structured snippets, business name, image assets) and a stated target (campaign or account). It also explicitly names the sibling google_ads_add_assets as the tool for sitelinks/callouts/calls, so an agent can disambiguate without opening either schema.

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 clearly routes sitelinks, callouts and calls to google_ads_add_assets, which is real when-to-use guidance against the closest alternative. It does not explain when to attach assets at account level versus campaign level, nor how it relates to google_ads_pmax_assets or google_ads_assets (read/listing), so the guidance is clear but not exhaustive.

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