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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the technical safety profile is covered. The description adds domain-level consequences beyond that: no inventory reservation and no advertiser charge, which is more concrete than a generic readOnly flag for an agent deciding whether this call has side effects. Auth requirements and rate limits remain unstated.

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 tight sentences with zero filler; the operative scope ('pricing and audience estimates') is front-loaded and the non-commitment caveat follows immediately. Nothing can be cut without losing information.

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?

An output schema exists, so return values need not be explained, and the annotations carry the safety profile. For a 20-parameter preview tool with two nested planning shapes (owned/partner vs. providerPlan), however, the description gives no routing guidance on which input mode to use, leaving a real gap against the tool's complexity.

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?

With 20 parameters, only 20% schema description coverage, and deep nested objects (providerPlan, targeting.audience, geography), the description was obligated to compensate and does not. 'Selected screens and channels' loosely gestures at screenIds and providerPlan.channels, but source, quoteId, providerPlan vs. owned/partner budgets, audience targeting and geography handling are never addressed.

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 names a specific verb (preview) and resource (campaign plan) and states exactly what is computed: native campaign pricing and audience estimates for selected screens and channels. It is clear and distinguishable in substance from siblings like create_campaign_checkout or prepare_campaign_booking, though it never explicitly contrasts itself with them.

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?

Sentence two ('does not reserve inventory or charge') implies a pre-booking, exploratory step, which is a usable signal about when to call it. However, no alternative sibling is named and there are no explicit conditions or exclusions, so the guidance stays implied rather than stated.

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