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

With no annotations, the description carries the behavioral disclosure burden and does well: it reveals the ledger default, the narrow default date window, and the skip-reason behavior for manager/closed/canceled accounts instead of metrics. It does not mention read-only status or output formatting, but it adds meaningful behavioral context beyond the schema.

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 with no filler; the core purpose and key constraints are front-loaded. Every clause carries useful selection and invocation 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 query tool with no output schema, the description explains the essential outcomes: metrics for valid customers and skip reasons for invalid ones. It covers defaults and eligibility constraints well, though it stops short of detailing the exact metrics response shape or how skip reasons are surfaced.

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 100%, so the baseline is 3. The description adds value by clarifying the default for source ('ledger by default') and the default window behavior for date_from ('narrow default window'), which are not fully explicit in the schema property descriptions.

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 identifies the tool's resource and scope: daily spend for a single enabled non-manager customer, with ledger default and a narrow default window. It also distinguishes this tool from siblings by contrasting it with manager/closed/canceled accounts that yield skip reasons rather than metrics. It lacks an explicit finite verb like 'query' or 'return', but the tool name and content make the purpose unambiguous.

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 implies when to use the tool: when the agent needs bounded daily spend for one enabled non-manager customer. It explains what happens for unsupported account statuses, but it does not explicitly name alternatives or state when not to use this tool versus siblings like google_ads_insights_overview_query.

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