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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the description's 'READ-ONLY' line is largely redundant. It does add one useful behavioral fact — brand_name appears in the report title — but says nothing about permissions, latency, or whether the report is generated on demand.

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?

One dense, front-loaded sentence that puts the tool's identity and the sibling alternative in the right order. It is information-rich rather than padded, though the em-dash stacking makes it slightly heavy for a single sentence.

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?

An output schema exists, so return values need not be spelled out, and the description still previews the KPI set. Combined with annotations covering safety, the definition is complete enough for an agent to invoke it 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 0%, so the description must carry parameter meaning and it only partially does: it explains brand_name's effect on the title and implies days through 'period performance' vs 'previous period'. customer_id (the required parameter) and the exact meaning/default of days are left undocumented.

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+resource (aggregates an account's period performance) and enumerates the exact outputs (cost/clicks/conversions/ROAS/CPA/CTR plus % change vs previous period). It explicitly distinguishes itself from the sibling client_report_link by labeling the latter the 'shareable page' option, so an agent can route correctly without opening a 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?

Gives a clear usage context (agency, white-label, client-ready) and names the alternative with a condition: 'For a shareable page, use client_report_link.' However it offers no when-not guidance (e.g., when a raw internal report is preferable) and does not describe account/period selection beyond defaults.

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