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

Annotations cover the safety profile (readOnly, non-destructive, open-world), and the description adds value beyond them: latency expectation (4-9s), the returned fields, and monetization behavior ('paid per call with x402; a failed call is not charged'). The billing and failure-charging disclosure is exactly the kind of operationally critical context an agent needs.

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?

Front-loaded with purpose, output shape and latency, then routing and usage rules — every sentence carries information. Minor redundancy: 'Read-only' restates the readOnlyHint annotation and could be dropped.

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?

Output schema exists, so return values need no further explanation, yet the verdict enum is still summarized helpfully. Latency, cost model, input format, and when-to-use alternatives are all covered for a one-parameter tool.

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% so the baseline is 3, but the description adds real semantic guidance beyond the schema: write the claim as a plain statement, keep it to one claim per call, and split compound claims. That constrains how the single string parameter should be composed.

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 ('Checks one factual claim'), names the output shape, and explicitly distinguishes itself from the sibling research.answer. An agent can select it without opening any schema.

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?

Gives explicit routing rules: use research.answer for open questions, split compound claims into separate calls, call once per claim for multiple claims. When-not and alternatives are both present.

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