Probe any URL to check for HTTP 402 A-Pay micropayment requirements, revealing exact price, currency, and payout receiver without spending funds.
Inspect an endpoint to check if it requires an A-Pay micropayment, inspect the exact price quote, currency, and payout receiver without spending any funds.
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | The URL to probe for HTTP 402 payment requirements |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden and does disclose the most important trait: this probe is free and non-destructive ('without spending any funds'), and it enumerates the information surfaced (payment requirement, quote, currency, receiver). It omits what is returned when no payment is required, auth needs, and rate limits, but the safety profile is clear.
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?
A single front-loaded sentence with zero waste; the no-cost guarantee and the enumerated outputs each earn their 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 one-parameter read-only probe with no output schema, the description covers purpose, the pre-spend framing, and the fields discovered. It would be fully complete with a note on the non-payment outcome, but nothing essential for correct invocation 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 coverage is 100%, so the single 'url' parameter and its HTTP 402 probing role are already documented in the schema. The description adds no format, validation, or syntax details beyond what the schema provides, so the baseline 3 applies.
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?
States a specific verb (inspect) and resource (endpoint) plus the exact data revealed: payment requirement, price quote, currency, and payout receiver. It implicitly separates itself from a paying sibling like apay_request via 'without spending any funds', but never names an alternative, so sibling differentiation is implied rather than explicit.
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 practical trigger (probe before committing funds) is implied by 'without spending any funds', which suggests the pre-payment inspection role. However, it never states when to use this over apay_request or that it should precede a payment, leaving the agent to infer the workflow.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.