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

With no annotations, the description carries full burden and discloses key behaviors: it's a paid operation ($5), one-time payment, key returned in response, no account/signup, batch enabled, and payment is conditional on receiving a result. Could mention error handling or idempotency, but current detail is strong for a purchase tool.

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 front-loaded with the core purpose and cost, then efficiently explains the two-step process. Every sentence adds necessary information without redundancy. No wasted words.

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 mentions the key arrives in the paid response and the first response contains an 'accepts' array. It doesn't specify exact response shapes, but provides enough for an agent to extract the needed data. Slightly lacking in response structure detail, but still robust.

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?

The single parameter 'x402_payment' is described in schema as 'base64 X-PAYMENT payload'. The description adds crucial meaning: explains it's used only in the second call and that its value comes from the first call's response. This goes well beyond the schema definition.

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 clearly states the tool mints a 30-day HostDeFi Agent-plan API key for $5, with specific call limits and batch capability. It distinguishes well from sibling tools (pricing, signals, alerts, etc.) which serve different purposes.

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?

Provides explicit two-step process: first call without x402_payment to get payment requirements, then pay and call again with x402_payment. It explains the payment flow and that you're only charged on success. Lacks an explicit note about alternatives (e.g., when to use get_x402_pricing instead), but the context is clear enough for an agent.

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