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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive, but the description adds crucial behavioral context: the distinction between could_not_verify (check did not happen, carries verification_error, must not be shown as evidence) and unsupported (looked but no source). It also reveals the internal routing logic and that it replaces multiple sequential calls, going far beyond what annotations provide.

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 somewhat long but every sentence earns its place: trigger phrases, usage scope, routing, return values, and critical caller warnings. It is front-loaded with examples and uses an 'IMPORTANT for callers' section to highlight a critical caveat. Slightly verbose but well-structured and information-dense.

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?

Despite having no output schema, the description fully explains return verdicts and error semantics, covers both parameter meanings, clarifies the difference between could_not_verify and unsupported, and outlines the routing logic. Given the tool's complexity, the description gives an agent everything needed to select and invoke it correctly.

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%, with both parameters (claim and tolerance_pct) well-described in the schema, including examples and semantics. The description reinforces the tolerance behavior (implied by wording, capped at 5) and mentions the claim parameter indirectly, but does not add new meaning beyond the schema. Baseline 3 is appropriate.

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 starts with explicit trigger phrases ('fact check', 'verify the claim that...') and a clear verb+resource: natural-language claim verification against authoritative sources. It distinguishes itself from sibling tools by framing it as a dedicated fact-check that replaces 4–6 sequential calls, making its purpose unambiguous.

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 explicitly states 'Use whenever the agent needs to check whether something a user said is factually correct' and then provides a routing rule: company-financial claims go to SEC EDGAR fast path, any other factual claim falls through to grounded pipeline. This gives clear when-to-use guidance and effectively covers the full scope, with no ambiguity about alternatives.

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