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

Annotations already declare it is a non-read-only, open-world, non-destructive write. The description adds the meaningful behavior the annotations cannot: the confirm=false dry-run switch and the hard requirement that at least one landscape + one square image + one logo be present. It does not say whether re-adding duplicates or how repeated calls behave beyond the idempotentHint flag.

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?

Every clause earns its place: purpose, eligibility stake, parameter meaning, aspect ratios, minimum requirements, and dry-run semantics, all front-loaded with 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 6-parameter write tool with an output schema (so return values need no explanation), the description covers the asset-type semantics, the resource-name source, the eligibility requirement, and the dry-run flag. It omits permission/auth requirements and what happens to previously attached images, which would round it out fully.

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 has to carry the load and largely does: it explains marketing_image (1.91:1), square_image (1:1), logo (1:1), states the values are asset resource_names from upload_image_asset, and defines confirm=false as dry-run. customer_id and asset_group_id are left purely to the schema, a minor gap given they are self-evident IDs.

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 and resource ('Attaches IMAGES to a Performance Max asset group') and immediately conveys why it matters. It also names the upstream dependency (upload_image_asset) and the sibling category (PMax asset operations) an agent needs to place it correctly.

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?

Gives a clear context for use (required for campaign eligibility, minimum asset mix) and explains the dry-run path via confirm=false. It stops short of naming alternatives or exclusions relative to update_pmax_assets / update_pmax_asset_group, which the agent must infer.

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