Audience performance

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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, so the safety profile is covered. The description adds real, non-obvious behavior: which audience categories appear, the per-row metrics returned, and the important caveat that PMax audiences may be missing entirely. No auth or rate-limit detail, but the PMax data-coverage caveat is the kind of trait an agent needs.

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, then returned fields, then the applicability caveat — a sensible ordering with little waste. The trailing 'Google Ads API: https://...' link is filler that doesn't help an agent select or invoke the tool, keeping it short of a 5.

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 explained, yet the description still names key metrics; all four parameters are fully documented in-schema and the PMax limitation is disclosed. Complete enough for correct invocation, with only the sibling-boundary question against get_demographic_targeting left open.

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%, including the date-range default behavior ('last 30 days if either is empty') and customer_id fallback, so the schema carries the parameter burden. The description adds no parameter-level meaning beyond what the schema already states, making 3 the correct baseline.

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?

Specific verb+resource: 'Get audience segment performance metrics', with the granularity (audience type) and returned fields spelled out. It distinguishes itself from generic performance tools by naming the audience-type dimension (USER_LIST, USER_INTEREST, AGE_RANGE, GENDER), but it never names the nearest-looking sibling, get_demographic_targeting, leaving some ambiguity between a performance report and a targeting-settings tool.

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 clear scope: 'Works for campaigns with explicit audience targeting (Search, Display)', and an explicit when-not: PMax audience targeting is automatic and 'may not appear in this report'. It stops short of routing the agent to an alternative tool for the PMax case.

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