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

Annotations already declare readOnlyHint=false and destructiveHint=false; the description usefully reconciles this by clarifying that it persists an internal plan while leaving advertising entities untouched, which is non-obvious for a non-readonly tool. What is missing is the plan lifecycle (expiry, validity window, what makes a plan confirmable).

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: purpose first, scope second, side-effect clarification last. No filler and no repetition of the title.

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?

Output schema exists, so return values needn't be explained, and annotations plus a rich nested schema cover the mechanics. The remaining gap is workflow positioning — which tool consumes the prepared plan and under what conditions — which an agent must infer from sibling names alone.

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 100% and the nested schema already documents operation limits, action types, selector semantics, and even the 'state goes in value, not action.state' gotcha. The description only restates the changeable fields (bids, states, names), so it adds little beyond the schema — baseline 3 applies.

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 (Prepares) and resource (an immutable, separately confirmable Amazon Ads plan) and scopes it to ad-group default bids, states, and names. The clause 'without changing advertising entities' implicitly separates it from apply_ad_group_changes, though that sibling is never 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?

Usage is implied by 'immutable, separately confirmable plan' — an agent infers this is the pre-apply step — but no explicit when-to-use/when-not or next-step guidance is given. The description never points to confirm_workflow_plan or apply_ad_group_changes, which matters in a family of ~10 prepare_*/apply_* pairs.

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