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

No annotations are provided, so the description carries the burden. It discloses the key behavioral trait: it returns either a zero-result answer or x402 payment instructions. However, it doesn't explain what x402 means, what happens after payment, or whether this is a read-only operation. The description adds meaningful behavioral context but leaves gaps.

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 and outcome. Every word earns its place, and the x402 payment instruction is a compact way to convey the tool's unique behavior.

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 tool with no output schema and no annotations, the description covers the core behavior but omits important context: what x402 means, how params affect the query, and what a 'zero-result answer' looks like. It's adequate for a simple probe tool but not fully 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 mentions 'shelf' and 'matching paid intelligence' but doesn't explain the 'params' object at all. The description gives no detail on how shelf_id or params should be structured, leaving the agent to infer from the schema alone.

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 a specific verb ('Probe') and resource ('a shelf'), and clearly distinguishes this from the sibling tools by framing it as a cost-free way to test whether paid intelligence exists. It doesn't explicitly name a sibling, but the contrast with 'matching paid intelligence' implies the distinction from search_intelligence.

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 implies when to use this tool: when you want to check a shelf without spending, and it hints at the alternative (paid intelligence retrieval). It doesn't explicitly say 'use search_intelligence instead when you want full results', but the zero-result vs x402 payment instruction contrast gives clear context.

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