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

Annotations already declare this is a non-read-only, non-destructive, non-idempotent, closed-world call; the description goes well beyond that by disclosing the no-auth exemption, the exact credential artifacts returned (there is no output schema), the human-approval handshake ('Show them the URL and code; they approve once'), and the side effect of creating a free account. That is precisely the behavioral context an agent needs to drive an interactive flow without surprises.

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 and dense, with the return contract stated before the parameter rules and the next step last — no filler sentences. The return-value clause ('returns approval_url and user_code for your user, and device_code for you') is slightly tangled and needs a re-read to parse which artifact belongs to whom.

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?

With no output schema, the description carries the return contract and does so fully: what is returned, who each artifact is for, what to do with it, and which tool to call next. For a 4-parameter initiation tool in an interactive flow, nothing an agent needs in order to call it correctly 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; the description earns extra by adding operational meaning the schema cannot express — that data_wanted and use_case must be inferred from the project/context and clarified with exactly one short question only as a fallback, and that found_us must never be guessed. It does not mention the 'agent' parameter at all, which is the one small 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?

States a specific verb and resource ('starts a signup') plus the concrete artifacts returned ('approval_url and user_code for your user, and device_code for you'). It also distinguishes itself from the sibling finish_signup by naming it as the required next step, so an agent can place it in the flow without opening any schema.

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 ('No key needed') and an explicit follow-up ('Then call finish_signup'), which is enough for an agent to know when this tool is the entry point. It does not state the inverse case — e.g. what to do if a key already exists or a signup is already in flight — so the exclusion side is implied rather than explicit.

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