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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=true, so the explicit 'Read-only' restates structured data. The real added value is the semantic disclosure of what an 'ad set' maps to per platform, which tells the agent what the returned entities look like conceptually. No pagination, rate-limit, or result-volume context.

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, front-loaded with the verb and scope, no filler. The second sentence is dense but every clause resolves a real ambiguity an agent would hit when switching platforms.

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 needn't be explained, and annotations fully cover the safety profile. The description's job here is concept normalization, which it does thoroughly; only minor gaps (pagination or result-size behavior for large accounts) remain.

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% and each parameter carries its own description, including the enum-like platform list and the account_id caveat (DV360 advertiser, Outbrain marketer). The description adds nothing parameter-specific beyond reinforcing single-platform scope, so 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 (ad sets) plus the constraint that it operates on one connected ad platform. The terminology mapping ('Ad set = Meta ad set, Google... ad group, X or DV360 line item, LinkedIn campaign') makes the resource unambiguous across all supported platforms, which no sibling tool does.

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 'one connected ad platform' scoping plus the hierarchy-normalization sentence gives the agent a clear context: use this to enumerate the mid-level entities under a campaign for a single platform, versus list_campaigns (above) or list_ads (below). It stops short of explicitly naming those alternatives or stating exclusions.

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