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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description goes beyond them by disclosing the +10% promo bonus (capped) and that the ANANSI rail is disabled in v1. That last point is important behavioral context, though cap value and quote validity/expiry are left unspecified.

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 short sentences, zero filler, with the scope statement and the availability constraint front-loaded. Nothing is repeated from the title or 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?

For a 2-param read-only quote tool with annotations covering the safety profile, the key omission is that there is no output schema and the description never hints at what the quote returns (price, bonus amount, expiry). Combined with the undescribed usd_amount, the definition is adequate but not complete.

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 50%: api_key is documented in the schema, usd_amount has no description. The description contextualizes the amount as a USD credit top-up but adds no units, minimum, or range beyond what the parameter name already implies. Baseline 3 is appropriate given partial schema coverage and no compensating detail.

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+resource (quote a credit top-up) and pins the payment rail to ANANSI, which separates it from generic siblings like quote_anansi and my_credits. It stops short of explicitly naming/contrasting the sibling quote tool, so it lands at clear-but-undifferentiated-from-named-alternatives.

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?

"Quote only: the ANANSI rail is OFF in v1" tells the agent this call produces no executed transaction and that the underlying feature is unavailable, which is real when-to-use context. However, it never routes the agent to an alternative (e.g. quote_anansi, buy_house_plan, my_credits) for actually acquiring credits, so usage is only implied.

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