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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so 'Read-only' adds nothing new. What does add value is the enumeration of returned fields, including the diagnostic 'whether they can serve (and why not)', which substitutes for the absent output schema and tells the agent this call surfaces troubleshooting data, not just names.

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?

One tight sentence front-loads the verb, resource, returned fields, and then closes with the read-only constraint. There is no filler or redundancy.

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?

All three optional parameters are schema-documented and the mutation/read profile is covered by annotations, but the description says nothing about result volume, pagination, or behavior when multiple accounts are enabled (where the schema's 'optional when only one is enabled' condition leaves a gap). For a listing tool that may return many campaigns, that omission matters.

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% with three fully documented parameters (folder, account, language), so the schema carries parameter meaning. The description adds no guidance about how account scoping or the card language affects results, leaving it at the documented-baseline level.

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 and resource ('List X Ads campaigns') and enumerates the fields returned (ID, status, serve eligibility and reason, daily and total budget), which lets an agent recognize it as a read-list tool for X Ads specifically. It does not explicitly contrast with nearby siblings such as x_ads_performance or x_ads_create_campaign, relying on the platform+verb naming to differentiate.

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 only implied through the verb 'List' and the 'Read-only' tag; there is no explicit statement of when to pick this over x_ads_performance (metrics) or x_ads_create_campaign/x_ads_set_status (mutations). An agent can infer the read/list role but must reason about alternatives itself.

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