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

The read-only and non-destructive behavior is already covered by annotations, but the description adds useful scope and output context: reachable accounts include MCC children, spentLast30Days is included, and plan_status appears only when the plan is at its limit. It does not fully describe the account object or list ordering/pagination, so it is strong but not complete.

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 description is four short sentences, front-loads the core scope, and then adds conditional output details without redundant wording. Every sentence contributes either purpose, usage, or return-value context.

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 list tool with no output schema, it explains the key discovery scope and highlights two important computed fields. It could be slightly more complete by mentioning the main account identity fields returned, but it is sufficient for correct invocation.

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?

There are no input parameters, so the baseline is 4 under the rubric. The description uses its space to explain returned fields rather than parameter semantics, which is appropriate here.

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 gives a specific verb and resource: it lists every Google Ads account the login can reach, including MCC client accounts. 'Start here' also signals its role as an entry-point tool among the account-related siblings.

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 clearly indicates initial use with 'Start here' and says to show spentLast30Days when the user picks an account. It does not explicitly contrast with siblings like switch_account or account_overview, so it falls short of full when/when-not guidance.

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