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

With no annotations, the description carries the full behavioral burden, and it does disclose real behavior: a human approval step via emailed link, an account-existence branch ('signing in first if the email already has an account'), and the fact that this is only half of a two-call flow. It does not say whether a key exists before approval, what happens on rejection or timeout, or what the call itself returns, leaving meaningful gaps for an unannotated mutation-adjacent tool.

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 tight sentences, front-loaded with the action, then the data-collection rule, then the approval flow and the handoff. No sentence is filler and the sequencing mirrors the actual workflow.

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 multi-step, human-in-the-loop flow the description covers prerequisites (ask the user, don't guess), the approval mechanism, and the required next tool. The main omission is what start_signup itself returns and how the agent should behave if the user never approves, though the absence of an output schema makes that a modest gap rather than a fatal one.

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 schema already documents all four parameters, which sets the baseline at 3. The description adds one genuinely useful semantic constraint by specifying that email and use_case must come from the user rather than being inferred, but it says nothing about the agent and sports parameters.

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 uses a concrete verb and object ('Start a key for your user') and immediately names the follow-up sibling finish_signup, so an agent can place it in the signup flow. The term 'key' is a little informal, but the pairing with finish_signup and the email/use_case parameters makes the intent unambiguous.

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 explicit operating instructions: collect the user's email and what they are building, and 'never guess' those values. It also states the next step ('then call finish_signup') and describes the approval gate the user must pass. It stops short of saying when not to use it (e.g., when a key already exists), so it falls short of a 5.

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