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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds real value beyond that: it names the exact subsystems probed and states that it returns per-service status plus actionable remediation guidance, which tells the agent this is a read-only probe that can be re-run freely. It does not mention cost, latency, or whether the check consumes quota against the ad platforms.

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?

The first two paragraphs are front-loaded and earn their place. The third paragraph is a block of three developer-documentation URLs that does little for tool selection and is internally inconsistent — Microsoft Advertising is named in the opening sentence but has no corresponding link. That tail is filler relative to the decision the agent needs to make.

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 zero-parameter diagnostic with an output schema and full annotation coverage, the definition gives what an agent needs: what is checked, what comes back, and when to reach for it. The only gap is operational context — whether it is cheap to call repeatedly or should be reserved for suspected outages.

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?

The tool takes zero parameters and the schema is a closed empty object, so there is nothing for the description to disambiguate. Baseline 4 applies; no parameter-level meaning is missing.

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?

Names a specific action and a concrete set of resources: tests AdLoop connectivity by checking the OAuth token, GA4 API, Google Ads API, and optionally Reddit Ads and Microsoft Advertising APIs. The scope is enumerated precisely, so an agent can tell this apart from data-fetching siblings like attribution_check or audit_ga4_property.

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?

"which makes it the diagnostic for failures in other tools" gives a clear when-to-use trigger, and "(when configured)" flags the conditional coverage for Reddit/Microsoft. It stops short of explicit when-not guidance or naming a specific sibling to run before/after, but the intended usage context is unambiguous.

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