inspect

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

Although annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, the description adds meaningful operational detail: it spends no money, sends no payment header, needs no API key or account, and is always safe. This goes well beyond the annotations.

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?

Three sentences with no wasted words. The core behavior and cost-relevant outputs are front-loaded, followed by safety guarantees and the explicit routing to 'pay'. Every sentence earns its place.

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 single-parameter, read-only inspection tool with rich annotations, the description covers what the tool does, what it returns conceptually, and when to invoke it. No important behavioral or usage information 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?

The input schema fully documents the single 'url' parameter with a clear description, so the baseline is 3. The tool description reinforces that the URL should be x402-protected but adds little parameter-specific meaning beyond the schema.

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 states a specific verb ('Fetches'), a specific resource ('x402-protected URL'), and the key scope ('WITHOUT paying'). It clearly differentiates from the sibling 'pay' by emphasizing that this tool reports price and requirements without spending money.

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 tells the agent to use this before 'pay' to know costs, which is clear usage context. It does not mention other sibling tools like 'check_payment_signal' or 'discover' as alternatives, so it lacks full when-not guidance.

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