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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: it discloses the 500-row cap, that complete=false signals more rows, how next_after/after pagination works, that an identical read within 30 seconds may be cached (data_age_seconds), that reads are free and don't count toward the monthly change limit, and that missing values are not zero. This is rich operational context an agent cannot get from annotations alone.

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?

The purpose and key constraints are front-loaded, but the prose is dense and redundant: 'Date ranges use the AD ACCOUNT time zone' is restated as 'Dates use the ad account time zone', and the optional-parameter list partly duplicates the schema. Several sentences are run-ons that bury the pagination contract mid-paragraph.

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 15-parameter, no-required-arg tool with no output schema, the description covers the essentials an agent needs: scope, time zone, currency, pagination contract, caching, and status-filter level constraints. Return-shape detail is limited (no output schema exists to compensate), but complete/next_after/data_age_seconds/notes give enough to consume results safely.

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, and 15 params each carry their own schema descriptions. The description still adds meaning the schema does not: money values are in account currency not minor units (relevant to min_spend), dates resolve in the ad account time zone, rows carry campaign/adset/ad ids at their level, and next_after must be replayed with identical other fields. This pushes it above the 3 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?

The description opens with a specific verb+resource: metrics for the ad account or an object inside it, and enumerates the returned measures (spend, impressions, CTR, CPC, CPM, reach, frequency, actions). An agent can tell what it produces without opening the schema. It does not, however, explicitly distinguish itself from siblings like performance_overview, performance_dashboard or meta_ads_read, so differentiation is left implicit.

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 gives contextual cues for specific parameters (e.g. when to use breakdowns, that hourly has no reach/frequency, that effective_status needs a non-account level, and that include results/value are not available at account level). But it never states when to prefer this tool over sibling read/performance tools, nor any prerequisite beyond 'from a read of this ad account'. Use guidance is implied rather than explicit.

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