google_ads_add_promotion_extension

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

With no annotations, the description must disclose behaviors. It only states the action ('add') without mentioning idempotency, error conditions, permissions, or side effects (e.g., whether existing promotions are overridden).

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?

Well-structured with a one-line summary, purpose paragraph, parameter list, returns line, and an example. Every sentence is informative, no fluff. The example is particularly helpful.

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?

Covers purpose, parameters, and returns (via example). Lacks behavioral details but includes an output schema (signal true). For a tool with 8 parameters, it is fairly complete, though usage guidance is missing.

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%, but the description provides detailed explanations for each parameter (e.g., customer_id format, occasion enum values, discount_modifier options). This fully compensates for the schema gap, adding significant meaning.

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?

The description clearly states the tool adds a promotion extension to a campaign, specifying the action and resource. It distinguishes from siblings by naming the specific extension type 'promotion extension' and explains its purpose (highlighting special offers).

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 explicit guidance on when to use this vs. other extension tools like add_call_extension or add_callout_extension. The description implies it's for promotions but does not specify conditions or alternatives, leaving the agent to infer.

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