l402_discover

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

With no annotations present, the description carries the full burden. It transparently explains the non-payment behavior ('without paying') and the nature of the operation ('probe'), which is a lightweight read. It lists the returned data (invoice, price, format). It does not disclose error handling or edge cases, but for a simple read-only probe, the key behavioral traits are covered.

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?

Two sentences, front-loaded with the core purpose. Every sentence earns its place: the first explains what it does and returns; the second gives a practical usage directive. No filler or redundancy.

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?

The tool is simple (2 params, no output schema), and the description covers the essential aspects: purpose, when to use, and what is returned (invoice, price, format). It does not detail potential errors or network behavior, but given the simplicity and the clear usage guidance, the description is sufficiently complete for an agent to select and invoke the tool correctly.

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 50% (only 'url' is described). The description mentions 'URL' but does not explain the 'method' parameter at all. The schema provides enum values (GET/POST) and a default, but the description adds no further semantics, such as when to use POST vs GET. This leaves the method parameter under-specified, and the description does not compensate for the gap.

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 tool's function: 'Probe a URL for L402 payment requirements without paying.' It specifies the verb (probe), the resource (URL), and the purpose (discover L402 payment requirements). It also names distinct outputs (invoice, price in sats, format), which distinguishes it from sibling tools like l402_pay and l402_payment_verify.

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 provides usage context: 'Use this before l402_pay to check the cost of accessing a resource.' This names the primary alternative (l402_pay) and specifies that this tool is a precondition. It clearly implies this is for checking cost before committing to payment.

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