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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds genuinely new behavior: the returned report is itself a payable x402 endpoint, that payment happens through the agent's own x402 client, and that unmonitored endpoints return 404 and are never charged. The billing and error behavior are exactly the kind of context annotations cannot convey.

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?

It is front-loaded with the purpose, then the return values, then the exclusivity condition and the 404 caveat — good ordering with little redundancy. It runs slightly long for one parameter, but every sentence carries information the agent needs.

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?

An output schema exists, yet the description still summarizes the return shape (report URL, price, network) and covers the purchase path and unmonitored-endpoint failure mode. For a single-parameter read tool, nothing an agent needs to invoke it correctly is missing.

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?

There is a single parameter and the schema already documents it at 100% coverage ('Full URL of the x402 endpoint you want the paid report for, including path'). The description only reinforces the 'one endpoint' scope without adding format or syntax detail, so the baseline of 3 applies.

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 gives a specific verb and resource ('Get instructions for buying the detailed paid report on one x402 endpoint') and enumerates exactly what the report contains (score breakdown, price quote, wallet/price history, test-payment results). It also explicitly states what the tool is not ('it doesn't buy the report itself'), which separates it cleanly from any purchasing sibling.

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?

It names the alternative (the free check_endpoint result) and the precise condition for escalation ('only when the free result isn't enough and the user wants the full history'). It also clarifies the reporting vs. buying boundary, so the agent knows this call alone won't complete a purchase.

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