l402_discover

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

With no annotations, the description carries the burden and does the important part: 'without paying' tells the agent this is a non-mutating probe, and the return contents (invoice, price in sats, format) are disclosed. It omits edge behavior such as what happens when the URL has no L402 challenge and whether any credentials are needed, which keeps it short of a 5.

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 tight sentences, with the core action and the non-paying guarantee front-loaded before the comparison to l402_pay. No filler.

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?

No output schema exists, so the description usefully enumerates what comes back (invoice, sats price, format flavor). For a simple 2-parameter probe this is nearly sufficient; only failure/edge-case behavior for non-L402 URLs is left implicit.

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%: both url and the method enum are already documented in the schema. The description adds no syntax, format, or constraint detail beyond that, 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 and resource ('Probe a URL for L402 payment requirements'), plus the key modifier 'without paying', and names the return values. It is clearly distinguishable from the sibling l402_pay, which actually spends funds.

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?

'Use this before l402_pay to check the cost of accessing a resource' gives an explicit ordering rule and names the alternative tool. The agent knows exactly when to reach for this instead of paying directly.

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