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

With no annotations, the description carries the full behavioral burden and excels: it discloses the $0.02 USDC payment, the required API key, the failure mode before payment, and that claim text is sent to an external search provider. This covers cost, authentication, error behavior, and data flow.

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?

Every sentence earns its place: purpose, result categories, prerequisite, and error behavior. The core function is front-loaded, and the total description is compact with no filler.

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 key behavioral aspects well: payment, key requirement, failure path, and what the tool returns. However, two parameter semantics are missing, so an agent cannot be fully confident in constructing a valid call, especially for optional fields.

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 explain the parameters, but it only implicitly covers `claim` ('factual claim') and says nothing about `freshness_days` or `preferred_domains`. An agent would have to guess their exact role and format, leaving two of three parameters underspecified.

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 action ('Checks a factual claim'), a clear resource (fresh web search evidence), and exact result categories (supported/contradicted/mixed/insufficient/stale with sources). It also opens with the paid nature, making the tool's purpose instantly identifiable and distinct from the unrelated crypto-analysis siblings.

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 provides strong operational context: it is paid, requires TAVILY_API_KEY, and details what happens if the key is missing. It doesn't explicitly name alternatives or when-not-to-use scenarios, but the unique claim-verification purpose makes the intended use obvious.

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