validate_ad_copy

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

With no annotations, the description carries the full burden and does well by disclosing the tool's offline nature, specific character limits (headlines <=30, descriptions <=90, paths <=15), and the CJK/full-width counting behavior 'matching the Google UI.' It does not detail return values or edge-case handling, but this is somewhat mitigated by the presence of an output schema.

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 compact and front-loaded. Three sentences each earn their place: the purpose, the usage timing, and the specific rules. No fluff or repetition of schema details.

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 simple validation tool with an output schema, the description covers purpose, timing, and detailed rules. It does not explain that headlines/descriptions are arrays or how invalid input is handled, but those are likely evident from the schema and output schema. Overall, it is sufficient for an agent to invoke 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 description coverage is 0%, so the description must compensate. It does by explaining the constraints for the key parameters: headlines and descriptions with their character limits, and paths with a limit. It does not explicitly name path1/path2, but 'paths' clearly maps to both. The explanation adds meaningful context beyond the raw 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?

The description states a clear action: 'Check ad copy against Google's character limits' with a specific resource (ad copy) and domain (Google). It distinguishes itself from siblings like validate_pmax_assets by focusing on character limits and by highlighting 'offline, no account' as a key differentiating context.

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?

The description provides explicit when-to-use guidance: 'Use this while drafting, before creating anything.' It implies this is a pre-flight check before account-level actions, but does not explicitly mention alternatives or exclusions, so it lacks the full when-not/alternatives detail needed for a 5.

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