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

Annotation Contradiction: annotations include idempotentHint=true, but the description says the tool 'never returns a key that already belonged to that address; it issues one for this purpose only.' This implies each call mints a new key rather than returning an existing result, so repeated calls with the same email would create new keys—contradicting idempotency. Apart from that, the description does disclose useful behavior such as emailing the key, owner notification, and the 30-day expiration.

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?

The description is tightly written and front-loaded with the core action, then followed by constraints, workflow, and safety guidance. Every sentence adds useful information and there is no redundant fluff.

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 one-parameter tool with no output schema, the description covers the workflow, user consent, quota, expiration, and the resulting key's use in the X-API-Key header. It is nearly complete, but the tension with the idempotentHint annotation leaves some ambiguity about what happens if the same email is submitted repeatedly.

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 100%, so the baseline is 3 because the schema already documents the email parameter. The description adds meaningful behavioral semantics beyond the schema: ask the user for their email, do not guess, and the key will be sent to that address, which helps the agent use the parameter correctly.

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 states a specific verb and resource: getting a free qd_ API key for an email address. It also distinguishes itself from the sibling market-data tools by explaining that the key covers all four of them, so an agent can clearly route a 'get a free key' request here rather than to a data tool.

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 description gives an explicit workflow: ask the user for their email first, then call the tool. It also gives clear prohibitions ('Do not invent an address') and practical context about no account/card/payment being required, making it obvious when this tool is appropriate.

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