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

Annotations cover the safety profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false), and the description adds substantial value beyond them: auth is required, api_key is returned only once, the key is scoped to that sub-account, usage counts against parent plan limits, and plan prices are unchanged. The idempotency behavior of client_id (same key returns the original workspace with api_key null) is also disclosed.

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 usage condition is front-loaded, followed by inputs, return shape, and behavioral caveats in compact sentences. Every sentence carries distinct information (auth, quota, idempotency, return fields, quota accounting, nesting limit) 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?

There is no output schema, but the description enumerates the return object ({id, name, inbox_quota, account_id, api_key, api_key_prefix, inboxes_used, created_at}) and flags the one-time api_key. Combined with the auth, idempotency, and billing caveats, an agent has everything needed to call this 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 coverage is 100%, so the baseline is 3, but the description adds meaning: inbox_quota is explained as the cap on inboxes the sub-account may hold, and client_id's reuse behavior is clarified with the extra detail that api_key is null on a replay. That goes beyond the schema wording.

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 states a specific verb and resource ('the signed-in parent account should give a project or another agent its own API key and a fixed inbox quota'), which clearly identifies it as a workspace/sub-account creation tool. This distinguishes it from siblings like cooper_create_inbox or cooper_list_workspaces, which operate on different resources.

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 gives a clear triggering condition (use when the parent account should provision a project or agent) and a hard constraint ('A sub-account cannot create another workspace'). It does not explicitly name alternatives such as cooper_create_inbox, but the resource boundary makes the scope unambiguous.

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