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

Beyond the readOnlyHint and openWorldHint annotations, the description adds useful behavioral context: it returns a synthesized verdict rather than raw data, and it enumerates the specific checks performed. It could also mention live-probe behavior or latency implications, but the annotations already establish the read-only safety profile.

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 compact and front-loaded: the opening sentence states scope and outcome, followed by clear usage guidance and pricing. Every segment earns its place, and the 'When to use' label makes the decision context easy to scan.

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?

For a simple two-parameter read-only tool, the description gives enough information to decide when to call it and what kind of answer to expect. There is no output schema, so the enumerated checks and 'verdict' help, though the exact return shape remains unspecified.

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 100%, so the schema already documents both 'resource' and 'probe_now' well. The description reinforces that the resource is the URL being considered for payment, but it adds little beyond what the schema provides.

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 concrete resource ('a single resource URL') and specifies the checks it performs: whether it is up, whether its 402 is well formed, what it quotes, and whether its payout address has been paid on-chain. It clearly communicates that the tool returns a verdict, but it does not explicitly distinguish itself from sibling tools.

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?

A dedicated 'When to use' section tells the agent to call this when it already has a URL and wants to know whether sending money is a good idea, and even gives a cost-benefit threshold. It does not explicitly state when not to use it or name alternative sibling tools.

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