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

Annotations already declare readOnly=true, destructive=false, and openWorld=true, so the safety profile is covered. The description adds real behavioral value beyond that: it discloses what is returned (client accounts under a manager) and the plan_status flag values (active, switch, locked), which matters because 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 short sentences, front-loaded with what the tool lists and immediately followed by the routing directive "Start here". Every sentence carries distinct information with 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 usefully describes the return set and the plan_status enum meanings. It omits auth/permission prerequisites (e.g. OAuth login requirement) and pagination behavior, but for a zero-parameter read-only listing tool it is nearly complete.

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, so the baseline is 4; there is nothing for the description to disambiguate. No parameter-level guidance is needed or 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?

States a specific verb (Lists) and resource (Google Ads accounts) with explicit scope: every account the login can reach, including MCC client accounts. This clearly differentiates it from siblings like account_overview and billing, which the agent can infer operate on a narrower view.

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?

"Start here" is a direct, actionable usage signal that positions this as the entry point for account discovery. It stops short of naming alternatives or stating exclusions (e.g. when to prefer account_overview), so it falls just short of a 5.

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