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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered. The description adds value by sketching the shape of each result row (type and select/filter/sort flags), but it says nothing about pagination, the default 300 / max 1000 cap, or cost/latency behavior – facts an agent would want before calling repeatedly.

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 sentences, zero filler. The output shape comes first and the usage cue second, which is the right ordering for a discovery tool an agent will chain into ads_query.

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?

With an output schema present, return values need no explanation, and the annotations plus short description cover purpose and sequencing adequately for a simple two-parameter read tool. The only real gap is that the `limit` parameter has no stated purpose in either the schema or the description.

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 with concrete examples (campaign, ad_group, keyword_view, metrics, segments) while `limit` carries only default/min/max constraints and no prose. The description corroborates that the target is a GAQL resource but adds no meaning beyond the schema, and never mentions the limit parameter at all.

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 and resource (list fields on a GAQL resource) and specifies exactly what is returned: type plus select/filter/sort capability. It explicitly positions itself relative to the sibling ads_query, so an agent can tell the two apart without reading either schema.

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 it before writing an `ads_query` on an unfamiliar resource" gives a clear triggering condition and names the dependent tool. It stops short of saying when not to bother (e.g. for well-known resources) or naming any alternative discovery tool, but the context is unambiguous.

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