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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is covered. The description goes further by disclosing the pre-send validation (operation kind, approval integrity, state drift) and the no-replay reconciliation rule for uncertain outcomes, which is genuine behavioral context beyond the annotations.

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 dense sentences, front-loaded with the action and then constraints and reconciliation rule. Every sentence carries information, though the phrasing is somewhat compressed.

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 destructive mutation tool with annotations covering safety and no output schema, the description supplies the missing prerequisites, validation behavior and reconciliation guidance. Return-value detail is absent but not required given no output schema exists.

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%; customer_id is documented and connection_context has a pattern, but draft_id is bare. The description partly compensates by defining draft_id semantically (a matching draft from the prepare tool), yet it adds nothing about connection_context or the format of the affected-campaign set.

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 (change) and resource (shared portfolio CPA or ROAS target) plus the exact scope (the complete explicitly listed set of affected campaigns). It is clearly distinguishable from its sibling google_ads_portfolio_target_update_prepare, which it names.

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 an explicit precondition ('After explicit approval') and an explicit source constraint ('Accepts only a matching draft from google_ads_portfolio_target_update_prepare'). The agent knows when this tool is valid and what input it will reject.

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