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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description still adds real value beyond them: the auth requirement and the explicit caveat that API keys are NOT returned even though api_key_prefix appears in the payload. No rate-limit or pagination behavior is disclosed, which keeps it at a 4.

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?

Four tight sentences: trigger, then safety/input constraints, then the exact return shape, then the one non-obvious exclusion. Nothing is repeated and the most decision-relevant information is 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?

There is no output schema, so the description carries the return-shape burden and does so inline with the full field list and the API-key exclusion. For a zero-parameter, read-only list tool this is exactly the information an agent needs.

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?

Zero parameters, so the baseline is 4. The description's 'no inputs' statement correctly confirms the empty schema and prevents an agent from inventing filter arguments.

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 (list) and resource (sub-accounts/workspaces) and pins down the scope as 'sub-accounts created by the signed-in parent'. That scoping phrase distinguishes it from sibling list tools like cooper_list_owners and cooper_list_inboxes without needing to inspect their schemas.

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?

Opens with an explicit when-to-use trigger ('Use this when you need the sub-accounts created by the signed-in parent'). It gives clear context but names no alternatives or exclusions, so an agent must infer that this is the right call over other list_* siblings.

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