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

With readOnlyHint already covering the safety profile, the description goes well beyond: it discloses sort order (cost descending), the 10,000-row cap with truncated=true, cursor pagination, and the subtle targeting_status states including the non-obvious 'a city inside a targeted country is none.' It even notes bid_adjustment_percent only appears when targeted and non-zero.

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?

Front-loaded with purpose and scope, then behavior, then routing and output fields. Information-dense with little waste, though the targeting_status and output-field sentences are packed tightly enough that it reads as a long single block rather than scannable segments.

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?

No output schema exists, and the description compensates by enumerating the returned row fields (location_id, impressions, clicks, cost, conversions, ctr, etc.). Combined with granularity semantics, truncation, and pagination, an agent has everything needed to call and interpret this 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 coverage is 100% so the baseline is 3; the description adds real meaning by defining granularity levels (region defaults to states/provinces, city is the most specific Google reports) and by tying location_id to the write siblings. It does not, however, expand on days/limit/cursor beyond the schema text.

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 resource (location performance) with two sharp scoping constraints: 'where the user actually was (not locations they showed interest in)' and 'Search campaigns only.' This separates it cleanly from geotarget interest data and from get_device_performance without opening 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?

Names concrete alternatives with the condition that selects them: set_location_bid_adjustments to change a targeted bid, and update_campaign_locations (add_exclusions/add_targets) with location_id to exclude or target. Routes the agent explicitly rather than leaving write-vs-read to inference.

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