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

The description adds genuinely valuable traits beyond the annotations: the key is shown only once (a critical one-shot disclosure the annotations don't convey), the free-tier quotas, the one-key-per-email uniqueness constraint, and the exact auth mechanism (x-api-key header or Authorization: Bearer). This goes well past the readOnly/destructive/idempotent hints.

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 tight sentences, front-loaded with purpose then the operational details an agent must retain (shown once, header format, uniqueness). No filler or repetition.

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?

There is no output schema, so the description carries the return-value burden and does so by warning that the key is displayed only once. Combined with quotas, auth header usage, and the uniqueness rule, an agent has everything needed to call this and persist the result correctly.

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?

With a single param and 100% schema coverage, baseline is 3. The description adds meaning by clarifying that the email is the key's owner and enforcing 'one key per email', which qualifies the schema's vaguer 'Where to reach you about the key' framing.

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 ('Creates a free YieldCave API key') and immediately scopes it with concrete limits (300 calls/day, 3 alerts, 7 days of history) tied to an email. It is unmistakably distinct from siblings like upgrade and manage_subscription, which are about billing/subscription state rather than issuing a key.

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?

Usage is implied rather than stated: the free-tier limits and the 'one key per email' rule suggest when this is appropriate, but there is no explicit when-to-use or when-not-to-use guidance and no named alternative (e.g., upgrade for higher limits). Adequate but leaves routing to inference.

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