create_sub_user

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

Goes well beyond the annotations by disclosing real behavioral facts: the call mutates the account, the password is generated server-side, and it is only returned in the response when the server permits revealing passwords, otherwise the user must read it in the dashboard. That conditional return behavior is exactly the kind of detail an agent cannot infer from readOnlyHint/destructiveHint/openWorldHint.

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?

Front-loaded with the purpose, then the password behavior, then the parameter caveat — a sensible ordering with little waste. 'Changes the account.' is an under-specified fragment but is short enough not to be a real cost.

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 two-parameter mutation tool with an output schema already covering returns, the description covers creation semantics, the auth/reveal caveat on the generated password, and the traffic_limit unit convention. Only username constraints and any account-level preconditions are 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 description coverage is 0%, so the description must carry the load, and it does for the non-obvious parameter: traffic_limit uses the same unit as list_sub_users' traffic_limit/used_traffic, and omitting it means no limit. The username parameter gets no treatment (format, uniqueness, or constraints), which is the only meaningful gap.

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?

Starts with a specific verb+resource ('Create a sub-user') and adds distinguishing detail not in the name: the sub-user gets 'its own proxy login.' This separates it from update_sub_user and delete_sub_user, though it never names those siblings explicitly.

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 intent (create a new sub-user) is implied by the verb, but there is no explicit guidance on when to use this versus update_sub_user, nor any prerequisites such as account plan limits or username uniqueness. The only conditional guidance given is parameter-level (omit traffic_limit for no limit).

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