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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds substantial behavioral context: it explicitly says the tool does not score or recommend, returns facts and named signals, and compares against a public listing. This goes well beyond the annotations and gives the agent precise expectations.

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 front-loaded with 'Free.' and then concentrates on the core purpose and behavioral traits. Every sentence adds value, and the exclusion 'does not score or recommend' is a meaningful, concise addition. No fluff.

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 two-parameter read-only tool with no output schema, the description fully explains what the tool returns (charges, wallet, network, comparison data, named signals) and what it does not do. There is nothing an agent needs to know to call this correctly that 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% for both parameters (url and method). The description does not add meaning beyond the schema, but the schema already documents each parameter adequately, so the baseline of 3 is appropriate.

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 ('probes') and resource ('x402 endpoint') and clearly differentiates from siblings by emphasizing 'before paying' and 'without paying'. It also distinguishes from Tollkit-related services, making it clear this is a standalone check tool.

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 gives strong contextual guidance: use it before paying, it's free, and it works for non-Tollkit services. However, it does not explicitly name alternative tools (e.g., get_service_info) or state when not to use it, so it falls short of perfect routing.

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