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

No annotations are provided, so the description carries the full burden. It does well: it explicitly states the return behavior (source-supported facts when retrievable, explicit removed/blocked/unreachable/unsupported/insufficient-evidence states) and states a strong behavioral guardrail: 'rather than inventing facts' – preventing hallucination. This is substantial disclosure for a tool with no 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 substantial sentence that front-loads the primary action and scope, then lists output behaviors. It is not overly verbose – every clause adds value. Minor inefficiency: the list of listing types is somewhat long, but it's still reasonably concise.

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 has no output schema, the description provides a compact but sufficient list of possible return states. It doesn't explain how the 'claim' is used in verification (e.g., whether it checks against the page content), but the high schema coverage compensates for some missing detail. For a 2-parameter tool with this complexity, it's fairly complete, though not exhaustive – e.g., doesn't mention timeout or what happens on network failure beyond 'unreachable'.

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 'claim' have descriptions in the schema. The tool description doesn't add much beyond the schema, but it does imply that the claim is about availability, price, or location which aligns with the schema description. Since the schema covers the basics, a baseline 3 is appropriate; the description adds no extra syntax or constraints beyond the schema.

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 verb 'Verify' and the resource 'public product, marketplace, classified, auction, or other listing'. It also specifies the timing ('immediately before an agent relies on it') which adds context. No sibling tools exist to differentiate from, so the role which adds a clear scope of what is verified compensates for lacking sibling differentiation.

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: immediately before relying on a listing. It does not explicitly mention when not to use it or alternatives (since there are no siblings). The guidance is clear enough for an agent to decide when verification is needed, but doesn't address edge cases like verifying non-public pages or when to skip verification.

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