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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuine value by disclosing the return shape (labels joined to their campaigns) where no output schema exists, but it says nothing about pagination, empty-label accounts, or how folder-scope aggregation behaves.

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?

A single front-loaded sentence with zero filler — the resource comes first and the campaign mapping follows. It is efficient but arguably too thin for a tool with three parameters and no output schema.

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 read-only, zero-required-parameter listing tool with full schema coverage and no output schema, the description covers the essential contract: what is listed and the label→campaign association returned. The missing piece is the relationship to google_ads_manage_labels and any pagination/limit behavior.

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%, so all three parameters (folder, account, language) are fully documented in the schema, including the folder-vs-account tradeoff and the enum for language. The description adds no parameter meaning beyond that, 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?

Specific verb+resource: 'List the account's labels' plus the extra scope 'which campaigns carry each label'. An agent knows exactly what it gets back. It does not name the sibling google_ads_manage_labels, so the read-vs-write boundary is only implied by the verb 'List'.

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?

No when-to-use or when-not-to-use guidance, and no mention of the obvious alternative google_ads_manage_labels (which presumably creates/assigns labels). The agent must infer from the name alone that this is the read path and that tool is the write path.

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