list_sub_accounts

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

Annotations only declare readOnlyHint=true, so the description carries the rest of the burden and does add real context: the authentication requirement, the environment variable needed, the restart step, and the negative fact that the login flow will not unlock it. It does not mention result size or pagination, but for a no-parameter read that is a minor omission.

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?

Two compact blocks with the behavior stated first and prerequisites second, so an agent sees the purpose before the setup caveat. Every sentence carries information; no filler or repetition of the tool name.

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?

An output schema exists, so return values need not be described, and the auth prerequisite — the main obstacle to a successful call — is fully spelled out. The only gap relative to a simple list tool is the absence of any note on result volume or ordering.

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?

The tool takes zero parameters, so there is no parameter meaning to add; baseline 4 applies. Nothing in the description mischaracterizes the parameterless calling convention.

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 and resource ('List every sub-account') plus a scope detail ('the primary one included') that separates it from single-account getters like get_sub_account or get_current_sub_account. It stops short of explicitly naming an alternative, so it is clear but not maximally differentiating.

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 an explicit precondition for use (needs a Proof account with PROOF_API_KEY set) and explicitly rules out one path ('start_login does NOT open this tool'), which is genuinely useful. However, it never says when to choose this over sibling list/get tools such as get_sub_account, so usage guidance is only partly covered.

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