google_ads_describe_resource

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

Annotations already mark this as readOnlyHint=true, so the agent knows it is safe. The description adds behavioral detail by explaining it queries GoogleAdsFieldService and returns a comprehensive field list with selectability, filterability, etc. It also mentions the purpose of preventing specific errors, adding context beyond the annotation. No contradictions.

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 moderately long but well-structured with Args and Returns sections. The opening line immediately conveys the core purpose. Each sentence adds value: it explains the service call, the return structure, and the use case. It is not overly verbose, though the Returns section could be condensed without losing key information.

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 tool with a single parameter and an existing output schema (which we don't see but the description covers), the description is complete. It details the return format explicitly, provides usage context (essential before querying), and gives examples. An agent can call this tool correctly without missing critical information. The output schema already exists, so the description need not explain return values beyond what it does.

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?

The input schema has no description for resource_name (0% coverage), so the description must compensate. It does so by providing examples ('campaign', 'ad_group', etc.) and stating it is the GAQL resource name. This is helpful, though it doesn't specify format constraints or enumerate all valid values. The examples give enough meaning for correct usage.

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 clearly states the tool's purpose: it retrieves the schema (fields, metrics, segments) for a GAQL resource, listing each field's properties. It is specific about the resource type and the data returned, which distinguishes it from sibling tools like google_ads_query (executes queries) and google_ads_list_resources (likely lists resources). The description is not a tautology and adds meaningful detail.

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 advises that this tool is 'Essential before composing GAQL on an unfamiliar resource,' which gives clear context for when to use it. However, it does not explicitly name alternative tools or state when not to use it, so it falls short of a perfect 5 but provides solid guidance.

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