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

The line "Only the fields you pass change" is genuinely useful partial-update semantics that the annotations do not convey. However, with destructiveHint=true, the description never states that overwriting targeting on a live ad set can reset delivery/learning, nor what permissions or state are required — real gaps for a mutation tool.

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 sentences, both front-loaded and load-bearing: the first scopes the resource and fields, the second states the partial-update contract. Zero 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?

For a destructive 12-parameter mutation with no output schema and sparse schema descriptions, the definition leaves key operational questions unanswered: how to obtain interest/audience IDs, whether arrays replace or append, and what happens to existing targeting defaults. The core contract is present but incomplete.

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 only 25%, so the description should compensate more. It does map loosely onto the undocumented params (locations→countries, interests→interest_ids, custom/excluded audiences), but adds no format detail (ISO country codes, interest ID lookup via meta_targeting_search, Advantage+ interactions), and says nothing about folder, account, or language.

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?

Clear verb+resource ("Change an ad set's targeting") plus an enumeration of the exact targeting dimensions it controls. It distinguishes itself implicitly from meta_update_placements and meta_update_budget by naming targeting fields, though it never names a sibling 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?

Usage is implied by the field list, but there is no guidance on when to use this versus meta_create_adset or meta_targeting_search, and no prerequisites (e.g., that the ad set must already exist, or that IDs must be resolved first). No exclusions or warnings about live-ad impact.

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