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

Annotations already declare readOnlyHint=false, idempotentHint=false, destructiveHint=false, and openWorldHint=true, so the mutation/safety profile is largely covered. The description adds that the object is created PAUSED by default and clarifies what cpcBid governs, which is useful context, though the PAUSED state is also encoded in the schema's status default. No auth or rate-limit detail is added.

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 short sentences, front-loaded with the core action and followed by two high-value defaults. Nothing is wasted, though the cpcBid sentence is largely redundant with the schema and the whole thing could be tightened to two sentences.

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 7-parameter mutation tool with no output schema and rich annotation coverage, the description covers purpose and the key default state. The schema's unusually thorough extraFields and validateOnly descriptions carry the remaining detail, so the description is adequate without duplicating them.

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 description coverage is high (86%), so the schema already documents name, cpcBid, status, campaignId, customerId, extraFields, and validateOnly. The description only lightly reinforces cpcBid's role as the default max CPC for keywords in the group, adding little beyond the schema. Baseline 3 is appropriate.

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: 'Create a Search ad group inside a campaign.' An agent can distinguish it from create_campaign and update_ad_group by the 'Create' verb and 'ad group' resource. It does not name a sibling alternative, but the purpose is unambiguous.

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?

No explicit when-to-use, when-not-to-use, or prerequisite guidance is given. The PAUSED-by-default note is behavioral, not routing guidance. The agent must infer that a campaign must already exist and that this is the create-vs-update path from the verb alone.

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