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

Annotations declare readOnlyHint=false, destructiveHint=false and openWorldHint=false, so safety is partly covered; the description's 'No Google mutate' usefully clarifies that the non-read-only flag reflects internal staging rather than an external write. It says nothing about whether an approval/task handle is produced, whether the prepared upload expires, or what permissions are required.

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, front-loaded with the action and input forms, with the scope-limiting 'No Google mutate' note kept to a fragment. No redundancy, though the clipped fragment style slightly reduces readability.

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?

With no output schema and no annotations explaining staging behavior, the description should say what preparation yields (e.g. a task/receipt id) and what the agent does next. It covers the input contract but leaves the outcome and confirm handoff unstated for a 5-parameter, 4-required tool.

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 only 20% (just customer_id), so the description must compensate. It does add real meaning for base64_data, which can be either raw base64 or a 'gdrive: selection_key' string, but filename, content_type and connection_context remain undocumented 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 and resource ('Prepare an image asset upload') plus the accepted input forms, which cleanly distinguishes it from the sibling google_ads_asset_upload_confirm. It does not explicitly name that sibling, but the prepare/confirm naming and 'No Google mutate' make the stage clear.

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?

Tells the agent two ways to supply the payload: raw base64 image data, or a 'gdrive: selection_key' obtained from creatives_list_cloud, which implicitly routes to that sibling for sourcing assets. It never states when not to use it or that a confirm step follows the prepare, so usage is only implied.

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