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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantive context beyond them: it reads the live campaign, returns an approvalHash, is free, launches nothing, and manual launch is independent of Ads Watch. It also warns that provider targeting/reporting capabilities vary, which is useful beyond the structured hints.

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?

Purpose and the key 'nothing is launched' reassurance are front-loaded, and each sentence adds a distinct fact (scope, source of truth, return values, cost, launch independence, platform variance). Slightly dense but 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?

With no output schema, the description appropriately names the return contents (targeting map, exact current budget, approvalHash) and the scoping limitation (no cities/radius). For a read-only preview tool this is close to complete, though required-param meanings remain thin.

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 only 17% across 6 params with 3 required, so the description carries much of the burden. It clarifies the semantics of the countries field (provider-returned ISO codes only, no cities/radius) and the returned budget, but leaves campaignId/accountId/adAccountId/adId meanings implicit.

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?

States a specific verb and resource: it previews the country targeting map and launch card for an existing campaign, and enumerates what comes back (targeting, budget, currency, status). This clearly differentiates it from launch/confirm siblings without naming them, so it's clear but not sibling-explicit.

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?

Gives real context: 'for an EXISTING campaign', 'Free; nothing is launched', and 'Manual launch does not require Ads Watch', which tells the agent this is the safe preview step before an actual launch. It does not name the confirm/launch sibling as the follow-on alternative, so it stops short of full when/when-not routing.

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