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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds genuine domain behavior beyond that: the trap that a campaign lacking location targeting defaults to Google's broadest reach rather than 'no targeting'. It stops short of describing the return shape/format, which matters given there is no output schema.

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 sentences, front-loaded with what is retrieved, then the contrast with the sibling, then the actionable recommendation. Every sentence earns its place with no redundancy or 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 read-only tool whose annotations carry the safety profile and with no output schema to explain, the description is nearly complete: it covers scope, sibling contrast, and a critical default-behavior warning. The only gap is the undocumented customerId parameter and any indication of the returned structure.

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 50%: campaignId is documented ('Campaign id from get_campaigns') but customerId has no description in either schema or prose. The description adds no parameter-level meaning at all, so it fails to compensate for the undocumented half of the parameters.

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 states a precise verb+resource: it returns the targeting controls (location, excluded devices, ad schedule, negative keywords) for a campaign. It explicitly distinguishes itself from get_campaigns by contrasting the structural fields that tool covers. An agent can tell exactly what this tool fetches versus the sibling.

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?

It names the alternative (get_campaigns) and its scope, then gives a concrete trigger: 'Check this before enabling any campaign meant for specific markets or hours.' It also explains the failure mode of skipping it (missing location targeting defaults to broadest reach). This is explicit when-to-use guidance tied to a real risk.

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