update_campaign

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

No annotations are provided, so the description carries full burden. It discloses that the tool itself is not live-verified, but the underlying call has been live-probed via a related pattern, giving agents a sense of reliability. It also clarifies that it only returns a draft, so no direct mutation occurs. However, it does not mention required permissions or what happens on failure, though for a draft tool these are less critical. Overall, it provides more transparency than typical.

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?

The description is two paragraphs: the first covers purpose and usage, the second is a verification note. It is front-loaded with the key operational info. The second paragraph includes technical jargon like 'blank()-built' that might be noise, but it is brief and provides trust context. Overall, it is efficient and does not waste words.

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 4-parameter tool with no annotations and no output schema, the description is fairly complete. It explains the draft-apply workflow, the tCPA constraint, and the verification status. It does not explicitly state what the response looks like (beyond 'returns a draft'), which is acceptable given the sibling confirm_and_apply exists. It also doesn't list prerequisites like campaign existence, but these are implicit. Minor gaps remain, but the description covers the essentials for an agent to call correctly.

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 0%, so the description must compensate. It maps the main parameters explicitly: budget (daily_budget), status with allowed values Active|Paused, and tCPA (target_cpa) with the constraint that it only works on PMax. This adds value beyond the bare schema. It does not detail value ranges for budget or units, but the essential meaning is conveyed. Given the low coverage, this is a strong effort, though not exhaustive.

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?

The description states the specific verb 'Draft' and the resource 'campaign update' with the exact fields (budget / status / tCPA). It explicitly differentiates from sibling update_ad_group by noting that campaign-level tCPA is only operative on PMax. This makes the tool's purpose unmistakable.

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?

It gives clear when-to-use guidance: tCPA at campaign level only for PMax, and for Search it directs to update_ad_group. It also explains the workflow ('Returns a draft; apply with confirm_and_apply'), telling the agent that this tool only drafts changes and another tool applies them. This is explicit routing and sequencing.

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