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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description still earns credit by disclosing two behaviors beyond the structured fields: that breakdown 'splits rows by that dimension' and that since/until overrides date_preset. It does not discuss pagination or result limits.

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?

Dense, front-loaded, and terse: it declares the metric set first, then formats the enum-like values compactly, and ends with the date-override rule. Every clause contributes information with no filler.

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, and all six parameters are addressed or self-evident (account_id is the only untouched one). Combined with the annotations covering safety, the definition is essentially complete for calling the tool, with only minor gaps like pagination/limits.

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 0%, so the description carries the full parameter burden and does so well: it enumerates all date_preset values, all level values, all breakdown values, and gives the YYYY-MM-DD format and precedence for since/until. This adds substantial meaning that the bare schema lacks.

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?

Opens with a specific verb+resource: 'Meta performance report' and names the exact metrics returned (impressions/clicks/spend/reach/conversion actions). It is clearly distinguishable from sibling reporting tools by the 'Meta' scope and the level/breakdown controls, though it never explicitly contrasts itself with a sibling like meta_reach_estimate.

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?

Usage context is implied by the parameter semantics (pick a date_preset or since/until, pick a level, optionally a breakdown) and the precedence rule 'If since/until are given, that date range is used instead of date_preset' is a genuine conditional. But there is no explicit when-to-use / when-not guidance or routing to an alternative reporting tool.

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