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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful scoping context by declaring the result is 'structure only' and excludes metrics, but says nothing about pagination, result caps, or ordering—relevant for a listing call against an openWorld API.

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, zero filler, with the returned-field list first and the disambiguation rule second. Every clause carries information an agent needs to select and scope the call.

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?

There is no output schema, so the description correctly compensates by enumerating the returned fields and flagging the absence of performance data. Combined with 100% schema coverage and read-only annotations, an agent has what it needs; only pagination/ordering behavior is left unstated.

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%, with both accountId and campaignId documented in the schema including provenance (from msads_list_accounts / msads_get_campaigns). The description's phrase 'a campaign's ad groups' reinforces that campaignId scopes the call but adds no format or edge-case detail beyond the schema. 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 and resource ('List a campaign's ad groups') and enumerates the returned fields (id, name, status, default CPC bid, network, language), so the agent knows exactly what this returns. It is clearly separable from msads_get_ad_group_performance, which it explicitly names.

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 an explicit routing rule: this tool is structure only, and msads_get_ad_group_performance should be used for results. That is a clear context signal with a named alternative, though it does not spell out the reverse case (when performance alone is insufficient and both calls are needed).

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