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

Annotations already declare readOnly, idempotent, and non-destructive. The description adds valuable operational context: 'without paying' (cost behavior), 'grade' (evaluation output), 'presence and traction' (data checks), and 'buyer-concentration caveats' (ranking limitations). No contradiction with 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?

The description is a single sentence, but every clause contributes substantive info (probe, grade, presence, rank). It is front-loaded with the key action 'Probe a public endpoint without paying'. It could be more pointed, but it's not verbose or redundant.

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?

Given the tool's complexity (5 parameters, multiple investigation targets), the description covers the main behaviors enough for selection and invocation. An output schema exists, so return-value detail is not needed. It could mention more about the grading scale or list criteria, but it remains adequately complete.

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 0%, so the description must compensate. It indirectly maps params: 'probe a public endpoint' suggests url and implies HTTP request (method/body), and 'rank licensed market matches' implies market_query/market_limit. However, body and method are not explicitly explained, leaving gaps in parameter understanding.

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 uses specific verbs ('probe', 'grade', 'check', 'rank') tied to a concrete resource (x402 v2 challenge, x402-list, licensed markets). It clearly differentiates from sibling tools by focusing on x402-specific preflight actions, leaving no ambiguity about the tool's purpose.

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 establishes clear usage context: probe a public endpoint without paying and evaluate x402-related properties. It implies when to use the tool (before paying for access, to preflight), but does not explicitly state alternatives or exclusions. This is clear context without formal when-not guidance.

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