ads_list_accounts

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

There are no annotations, so the description carries the behavioral burden. It discloses an important environment-dependent behavior: the result set changes depending on whether GOOGLE_ADS_LOGIN_CUSTOMER_ID points to an MCC account or not. As a listing tool, 'List' and 'available to use' also convey a read-only, no-mutation operation, which is sufficient for this simple scope.

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 concise sentences, each earning its place: the first states the core purpose, the second explains environment-scoped behavior, and the third gives the use case and next-step value. The most important action and resource are front-loaded.

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 no-argument discovery tool with an output schema available, this description is nearly complete. It explains the data returned, the environment variable that changes behavior, and how the output should be used. It could explicitly mention that this is a read-only operation, but the verb 'List' and the phrase 'available to use' make that sufficiently clear.

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 has zero parameters, so parameter explanation is unnecessary. The description still clarifies what the tool returns (customer ids and names), which is more relevant than input semantics here. The 0-parameter baseline of 4 is appropriate.

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 opens with a specific action and resource: 'List Google Ads accounts (customer ids + names) available to use.' It also states the exact output shape (customer ids and names) and positions the tool as the discovery entrypoint for other tools, which clearly separates it from siblings like ads_get_account_details or ads_run_gaql.

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?

The description gives concrete guidance: when GOOGLE_ADS_LOGIN_CUSTOMER_ID points to an MCC, the tool returns the full manager tree, and otherwise it falls back to directly accessible customers. It also says 'Start here to discover the 10-digit customer_id for other tools,' which tells the agent the correct first step. It doesn't explicitly mention when not to use sibling tools, but the context is strong.

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