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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds genuine behavioral context beyond that: it never executes against Google and its local compatibility verdict is explicitly NOT equivalent to Google's validateOnly, which tells the agent how much to trust the result. It does not describe the output shape, keeping it below 5.

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 written sentences with the core action front-loaded and the limitation following immediately; nothing is wasted. It is arguably too terse given the complexity of the nested body object, but structurally it is clean.

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?

There is no output schema, and the description does not say what a preflight returns (errors, warnings, a pass/fail flag) or how to interpret a failure, which matters for a validation tool. It does adequately convey the tool's scope and the fidelity caveat, making it minimally viable for a nested-object tool.

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 only 33%: customer_id is documented, but the nested body object and connection_context carry only patterns and limits with no prose. The description explains none of these parameters (e.g. what 'resource'/'fields' should contain, or what connection_context is for), so it fails to compensate for the low coverage.

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 specific verb ('check'), the resource ('a bounded query'), and the key scoping constraint ('without executing it'), which distinguishes it from the actual query-execution siblings like google_ads_deep_analysis_query. It stops short of naming any sibling or clarifying what 'native field metadata' concretely covers, so it is clear but not maximally discriminating.

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?

Use is only implied: the name and 'without executing it' suggest running this before a real query. The second sentence ('Local compatibility is not Google validateOnly') is a useful disambiguation caveat, but there is no explicit statement of when to prefer this over google_ads_field_metadata or the query tools, nor any exclusion.

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