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

Annotations already declare readOnly=false/destructive=false, and the description usefully adds that this performs full provider validation without uploading or linking, clarifying the tool is a validating dry-run rather than a side-effecting mutation. It does not describe the returned handle/state that the confirm step would consume, leaving a moderate gap.

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 tight sentences with the asset-type list and the no-side-effect disclaimer front-loaded. Dense but every clause carries information; 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 prepare step over a six-way oneOf schema with no output schema, the description covers purpose, scope and prerequisites but omits the prepare→confirm contract and what the prepared artifact is. Adequate as a minimum-viable definition, not fully self-sufficient.

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 only 33%, so the description must compensate, and it does partially by naming the six asset kinds that map to the body discriminator and noting 'unlinked' and 'English structured snippet'. It adds no field-level meaning for the per-kind required properties, so it only partly covers the gap.

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 (prepare) and resource (typed unlinked extension asset) and enumerates the six supported kinds, which cleanly separates it from the link/unlink and create_confirm siblings. It stops short of naming those siblings explicitly, but the scope is unambiguous.

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 prerequisite context ('Requires extension flag and migration') and a negative constraint ('no implicit linking or upload'), which frames when it is applicable. However, it never states the workflow relationship to google_ads_extension_asset_create_confirm or when an agent should prefer prepare over a direct create.

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