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

Annotations already declare a safe read profile (readOnly, idempotent, non-destructive, openWorld), so the description needn't repeat safety. It adds the returned metric set and the default-level behavior, but says nothing about pagination limits or auth scope. Adequate but not rich.

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 tight sentences, front-loaded with the metric content, then the level guidance. No filler. Slightly under-uses its length budget given the tool's parameter surface, but nothing is wasted.

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?

With no output schema, listing the returned metrics is a useful completeness contribution. However, for a 6-parameter reporting tool with date-range and limit semantics, it omits date defaults, pagination behavior (limit max 500), and the since/until relationship, leaving gaps an agent would want filled.

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 50%, the threshold where the schema carries roughly half the load. The description adds a semantic hint for 'level' (default to campaign unless finer grain), but leaves limit, since/until interaction, and date_preset defaults unexplained beyond what the schema documents.

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 resource and scope: Facebook/Instagram ad performance with an enumerated metric list (spend, impressions, clicks, CTR, CPC, reach, conversions). An agent can tell it apart from the Google-side ads_report and from meta_list_campaigns, though it does not name those siblings explicitly.

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?

'Use level campaign unless asked for finer grain' gives real guidance for the level parameter, but it addresses how to call the tool rather than when to prefer it over siblings like ads_report, ga4_report, or meta_list_campaigns. Context is implied, not spelled out.

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