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

Annotations already declare non-read-only, non-destructive, open-world behavior, and the description adds genuinely new facts: it's free, the credit allotment, and the one-key-per-email constraint. It does not say what the response contains or what happens on a duplicate request for the same email, which is the remaining gap.

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?

Three short sentences, front-loaded with cost and trigger, then the constraint. No filler and nothing repeated from the schema.

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 and no annotations covering return values, the description should ideally hint at what comes back (the key itself, validity window). It conveys the key facts an agent needs to decide to call it, but leaves the response shape implicit.

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 67%, and the description meaningfully reinforces the email parameter (work email, ask the user, never invent one). However, 'name' and 'use_case' carry no description anywhere, and the description does not compensate for them, so the baseline 3 is appropriate.

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?

Names a concrete verb and artifact ('issues a trial API key') and quantifies the grant (2,000 credits a month), which is enough to distinguish it from the paid-check siblings that consume credits rather than create access.

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 trigger ('Use when the user wants to use Factline's paid checks without a crypto wallet') plus an operational rule ('Ask the user for their email first; never invent one'), so the agent knows both when to call and how to prepare the call.

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