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

With no annotations, the description carries the full burden and discloses key behavior: the router is free, the returned endpoint is live and re-checked seconds ago, payment terms are included, and a missing route yields null. It does not cover rate limits or whether any side effects exist, but for a read-side discovery tool this is substantial disclosure.

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 and fits into one dense but informative sentence. Every clause contributes to explaining what the tool returns and how it behaves, though the phrasing is slightly marketing-heavy rather than purely operational.

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?

Given the tool's simplicity, one required parameter, no output schema, and no annotations, the description explains the important return elements: the live endpoint, exact request, payment terms, and checked_now freshness. It is complete enough for an agent to call the router correctly, though it does not describe the response shape in detail.

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 100%, so the input schema already documents the single `need` parameter. The description adds useful examples such as web search, bitcoin price, and weather forecast, giving the agent concrete value guidance beyond the schema, though it does not specify format constraints.

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 uses a specific verb and resource: it routes a plain-language need to the ONE live paid x402 endpoint. It also distinguishes itself from direct data tools by emphasizing that it returns an endpoint, exact request, and payment terms rather than the underlying data.

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?

The description gives clear usage context: give one need in plain words and receive a live paid endpoint. It also explains the null case. However, it does not explicitly route the agent away from direct siblings like web_search or weather_forecast when those tools would be more appropriate.

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