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

Annotations already flag destructive and open-world, but the description adds the key operational facts: the two-step preview/confirm handshake for increases, immediate execution for decreases, and a hard block on budgets above the user's daily cap. That is exactly the non-obvious behavior an agent needs before mutating a budget.

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?

Four short sentences, front-loaded with the action, then the conditional workflow, then the guardrail. No filler and no restatement of the tool name or annotations.

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 5-parameter mutation with no output schema, the description covers the risky path (increases) and the preview return well. It is slightly incomplete on what the preview contains and on when to prefer budget-planning tools over an actual change.

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 60%, and the description compensates meaningfully by explaining that daily_budget is in account currency and that confirm=true must only follow explicit user approval, giving the confirm parameter real procedural meaning. It says nothing about reason or the optional account parameter, leaving that half to the schema.

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 ('Change a campaign's daily budget') plus scope ('in the account currency'), which is enough to separate it from google_ads_update_campaign, google_ads_budget_plan, and budget_status without opening any schema.

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 explicit when-behavior for both directions: decreases go through immediately, increases require a preview-then-confirm loop. It does not route the agent to alternative planning tools (google_ads_budget_plan, budget_pacing_plan) when the user is only exploring numbers, so it falls short of full when/when-not guidance.

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