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

Adds substantial context beyond the annotations: the API key's fullKey is returned exactly ONCE and cannot be retrieved again, the key never outlives the calling key, sub-workspace keys are rejected, and a plan requirement applies. These are operationally critical facts an agent cannot infer from openWorldHint/idempotentHint/destructiveHint.

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 sentences, each carrying distinct load: what is created, the one-time key disclosure hazard, and the authorization/plan constraints. Front-loaded with the core action and 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?

No output schema exists, so the description properly carries the return-value burden by explaining fullKey's one-time disclosure. For a two-parameter creation tool with full schema coverage, nothing needed for correct invocation is missing.

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 real meaning by stating the key is minted by default and is read & write bound to the new workspace, clarifying the generateApiKey side effect beyond the schema's brief 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?

States a specific verb (creates) and resource (sub-workspace under the account's main workspace) with a concrete use case ('one per client, for an agency'). It also implicitly distinguishes itself from the sibling create_workspace_api_key by explaining what the creation produces.

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?

Gives clear context and prerequisites: must be called with the main workspace's key, sub-workspace keys are refused, and it is a Professional-plan feature. It does not explicitly route to sibling tools like create_workspace_api_key for separate key minting, so it stops short of full alternative guidance.

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