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

Annotations cover the safety profile (readOnlyHint=true, openWorldHint=true, destructiveHint=false), and the description goes further by naming the returned payload fields (category, metrics, segments, related resources). With no output schema, that content disclosure is genuinely additive, though it omits anything about lookup failure behavior for unknown resources.

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?

Two tightly packed sentences: the first defines the operation and payload, the second states the downstream purpose. No filler, and the core purpose is front-loaded.

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 read-only metadata lookup with no output schema, the description adequately covers what the tool returns and why it exists. The only shortfall is silence on the optional `customerId` and on behavior for invalid resource names.

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 50%: `resource` is documented in the schema with its own examples, and the description merely repeats example values ('campaign', 'ad_group'), adding no new format or nesting guidance. The undocumented `customerId` is not explained in the description either, so the coverage gap is not compensated.

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 ('Describe') and resource ('a Google Ads API resource type') with concrete examples, and enumerates exactly what the response contains: category, selectable metrics/segments, related resources. This sharply distinguishes it from run_gaql_report, which consumes its output rather than producing metadata.

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?

Explicitly ties the tool to a downstream purpose ('Helps construct GAQL for run_gaql_report'), which tells the agent when to reach for it. It does not state when NOT to use it (e.g. skip it if you already know the resource schema), but the context is clear enough to route correctly.

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