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

Annotations already declare write, non-idempotent, open-world and destructive, and the description adds the crucial blast-radius clarification: 'Alerts only; a rule never pauses or changes a campaign.' That tells the agent the mutation is additive monitoring rather than campaign control. Remaining gaps are minor: no mention that repeat calls create duplicate rules or what permissions are needed.

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?

Three dense sentences, front-loaded with the [write] tag and the verb+resource. Every clause carries decision-relevant information — type semantics, scope requirements, and the alerts-only constraint — with no 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 seven-parameter mutation with no schema descriptions and no output schema, the description covers nearly everything needed to construct a correct call. It stops short of describing the created rule's identifier or return shape, which an agent may want before chaining into list_ads_rules or edit_ads_rule.

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 0%, so the description must carry the load, and it largely does: it names the two rule types and defines threshold semantics for each (impressions/reach ratio vs percent deviation from average CPL), enumerates the three scopes with the ID/UUID each requires, and flags ALL as default. It does not explain when to prefer an integer ID over the UUID variant.

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?

Opens with a specific verb and resource ('Create an ad monitoring rule that raises alerts'), which is far more informative than the title alone. It does not explicitly differentiate from the generic create_rule or create_website_rules siblings, but the 'ads' qualifier and the rule-type vocabulary make the domain obvious.

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?

Supplies conditional guidance inside the tool (scope ALL/ACCOUNT/WEBSITE and which ID each requires), which is genuinely useful when configuring a call. However, it never says when to reach for this versus edit_ads_rule or the generic create_rule, nor does it state prerequisites such as an existing ads account.

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