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

Annotations only state readOnly=false, destructive=false, openWorld=false. The description adds substantive behavior beyond that: it runs Google validate-only, takes a complete affected-resource snapshot, saves a private draft, and does not send the change. For a mutation tool this is exactly the side-effect disclosure an agent needs.

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 sentences, all informative, with the action and the non-execution guarantee front-loaded. Slightly dense but no filler; each sentence carries a distinct fact (action, behavior, gating).

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 tool with no output schema, the description covers the workflow, what is stored, and the confirm gating. It leaves unstated what the returned draft/lookup handle looks like and the role of connection_context, which is a minor gap.

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 carry weight. It does add some meaning (CPA vs ROAS target, the complete explicitly listed campaign set), but it never explains strategy_id, the numeric range constraints, or how body members interact. The nested schema's enums/patterns do much of the work, leaving baseline 3.

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+resource+scope: 'change a shared portfolio CPA or ROAS target for the complete explicitly listed set of affected campaigns.' It is cleanly distinguishable from its prepare/confirm siblings (e.g. google_ads_bidding_update_prepare) because both the resource and the staged nature are named.

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?

Explicitly names the follow-up tool (google_ads_portfolio_target_update_confirm) and states the gating condition: 'execution requires the user's agreement in the conversation.' The two-phase workflow and its prerequisite are stated, not inferred.

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