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

With no annotations, the description carries the full burden and does so well: it discloses that the tool calls the URL once, sends no payment, requires no authentication, is free, and grades specific aspects of the 402 response. It also explains what it returns, making the tool's behavior and side effects transparent.

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 detailed but every sentence earns its place: usage context, behavioral specifics, grading criteria, and parameter guidance are all covered without padding. The most important usage framing is front-loaded.

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 complexity, sparse input schema, and lack of annotations, the description is complete enough: it covers inputs, side effects, safety expectations, and the output shape. The output schema provides structural return details, so no critical guidance 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?

Schema description coverage is 0%, but the description fully compensates by explaining that url should be the full endpoint URL and that method is the verb the endpoint expects, limited to GET or POST. This adds meaningful guidance beyond the bare 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 names a specific verb ('Check') and a specific resource ('one x402 endpoint'), and explains the two use contexts: before paying or before shipping your own. It is clearly distinguishable from sibling tools because it is scoped to grading an endpoint's 402 response, not general payment readiness.

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 explicitly states when to use the tool: before trying to pay an endpoint or before shipping your own endpoint. It does not name sibling alternatives or state when not to use it, so it stops short of a 5, but the usage context is clear and actionable.

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