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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. Because there is no output schema, the description's enumeration of returned data (rate card, live rate, discount, reference-size estimates) adds real behavioral value beyond annotations, though it says nothing about freshness/rate limits or why two private keys are accepted by a read-only call.

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 sentences, zero waste, with the payload contents front-loaded and the sibling routing placed immediately after. Every clause earns its place.

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, the description correctly takes on the burden of describing return values, and it does so concretely. Safety is covered by annotations and credential usage is covered by the schema, so an agent has everything needed to invoke this 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?

Schema description coverage is 100% and both parameters carry detailed guidance in the schema, so the baseline is 3. The description adds no parameter-level meaning at all, notably not explaining why a read-only pricing call needs fluxIdPrivateKey and paymentPrivateKey.

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 specific verb+resource ('Returns the current USD rate card') and enumerates exactly what is included: live FLUX/USD rate, pay-in-FLUX discount, and instant USD estimates. It also explicitly separates itself from the sibling flux_quote_app, so an agent can pick between them without opening a schema.

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?

States the alternative tool by name and the condition that selects it ('Use flux_quote_app for the exact price of a specific app'). This is an explicit when-to-use-this vs when-to-use-the-other routing rule, leaving nothing to inference.

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