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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds real behavioral value beyond that: the reachability scope (direct or via Business portfolio) and the fact that returned adAccountIds are the input to all other ads tools.

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 with zero filler. The core purpose is front-loaded and the downstream-usage note follows immediately.

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, the description usefully signals the identifier format returned (act_<digits>) and the discovery role of the tool. It omits pagination or result-shape detail, but the essential calling context is present.

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% and both parameters (accountId, profileId) are documented in the schema with defaults. The description adds no parameter-level detail beyond noting adAccountId format, so the baseline 3 applies.

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 (List) and resource (Facebook ad accounts) with the scope qualification 'the connected Facebook account can reach, directly or through a Business portfolio.' This clearly separates it from ads_get_account and ads_list_businesses.

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 second sentence gives strong contextual guidance: every other ads tool needs an adAccountId obtained here, making this an upstream discovery call. It doesn't explicitly name a sibling alternative (e.g., ads_list_businesses) or state when-not to use it, so it falls just short of a 5.

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