discover_services

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

No annotations are provided, so the description carries the full burden. It discloses that the tool lists APIs with pricing, endpoints, and payment networks, giving some sense of return content. Yet it does not mention authentication requirements, side effects (though likely a read-only listing), rate limits, or any other behavioral constraints. This is adequate but lacks depth.

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 two sentences long, front-loaded with the core purpose, and every word earns its place. The second sentence gives a clear call to action. No unnecessary detail or repetition.

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 (no parameters, no output schema, no annotations), the description covers the essential context: what it lists and when to call it. It is sufficiently complete for an agent to use it effectively, though more detail about return format would slightly improve it.

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 tool has zero parameters, so the baseline is 4. The description is not required to explain any parameters and adds value by describing what the tool returns, but since there are no params to describe, no further param semantics are needed.

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 verb 'List' and the specific resource 'x402 Engine APIs', with details on what is listed (pricing, endpoints, payment networks). It distinguishes itself from sibling tools by being a discovery service, and includes a direct usage cue ('Call this first').

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 explicitly tells the agent to call this tool first to understand what's available, providing clear context for when to use it. However, it does not mention alternatives or explicitly state when not to use it, so it doesn't earn a 5.

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