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

With no annotations, the description does real work: it discloses that the spend cap is debited before any creation and that nothing is created above the cap, plus the connected-account precondition and the no-creative-writing guarantee. Still missing are the failure/refund behavior when a cap is hit mid-flight, idempotency, and what the caller gets back.

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?

Four short sentences, front-loaded with the operation and the spend-cap constraint. The idiom 'named out loud' is evocative but slightly informal; nothing is wasted, though a touch more precision would help.

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 an 11-parameter mutation with no annotations and no output schema, the description covers the safety-critical spend-cap behavior well but leaves gaps: channel/currency scope, daily_budget interplay with the cap, and return value (e.g., a plan id usable with get_ad_plan/stop_ad_plan) are unaddressed.

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 82%, so the schema already documents cap_minor, currency, channel, and the creative fields. The description reinforces the cap semantics ('the number the owner approved') but adds nothing about the other 11 parameters such as daily_budget_minor, country, or call_to_action. Baseline 3 is appropriate.

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 first sentence names a specific verb and resource ('Run one ad on one channel') and the sibling set (get_ad_plan, list_ad_plans, stop_ad_plan) makes the create-vs-read-vs-stop distinction clear. The line 'this never writes an ad' is a useful clarification about creative generation, but in isolation it reads as if the tool does not create an ad at all, which slightly muddies the purpose.

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?

'Needs a connected ad account' gives a prerequisite, and 'Run one ad on one channel' implies a single-ad scope. But there is no explicit when-to-use/when-not guidance versus get_ad_plan or stop_ad_plan, and no mention of what to do instead if the account is not connected.

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