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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description goes beyond annotations by explaining that it lists accessible customers beyond the MCC hierarchy, enriches results with specific fields, and supports bulk execution. This adds meaningful non-obvious behavioral context.

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 compact, front-loaded with the core purpose, and every sentence adds value. It packs the API method, scope caveat, enriched fields, cross-tool usage, and bulk support into two tight paragraphs 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?

Despite having no output schema, the description lists the enriched fields returned for each customer (descriptive_name, currency_code, time_zone, manager flag, status), which is essential for downstream use. With all parameters optional and safety annotations present, the description gives sufficient context for an agent to select and invoke the tool correctly.

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 description coverage is 0%, so the description carries the full burden for parameter meaning. It explains `customer_id` as a 10-digit identifier to reuse in other tools, `account` as the MCC connection selector, and `customer_ids` for batched execution. All three parameters receive meaningful semantics despite the bare input schema.

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 uses a specific verb ('List') with a clear resource ('all Google Ads MCCs and ALL customer accounts the OAuth token can access') and explicitly distinguishes this from a hierarchy-only listing by referencing customers:listAccessibleCustomers. It clearly differentiates from sibling tools by focusing on account enumeration rather than campaigns, ads, or keywords.

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 provides clear context on when the tool is useful: any time you need the full set of accessible customer accounts for an OAuth token. It also gives actionable guidance for downstream use of returned `customer_id` and `account` values, but it does not explicitly state when to prefer this over alternatives or when not to use it.

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