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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior. Beyond that, the description adds valuable context: it explicitly states the tool is free, read-only, has no side effects, and discloses that every request is recorded and analyzed in aggregate. It also promises an 'honest answer when it cannot' corroborate, which is useful open-world nuance.

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 compact and front-loaded: first sentence states the purpose, second gives when-to-use and return behavior, third covers privacy. It has minimal filler, though it slightly repeats the annotation's read-only hint. Overall it is efficient and well-structured.

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?

With no output schema, the description adequately summarizes what the tool returns: 'whether it can be corroborated from sources today, what evidence would come back, and an honest answer when it cannot.' It also explains the purpose, usage conditions, and privacy implications. It does not detail the unsupported-claim callback flow, but the schema covers the callback_url parameter, so the description is reasonably complete for a tool of this complexity.

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?

The input schema has 100% coverage with detailed descriptions for all 9 parameters, so the description does not need to explain each one. The description adds no per-parameter semantics beyond what the schema already provides, which fits the baseline of 3 for high schema coverage.

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 opens with a specific verb+resource: 'Check whether a fact can be corroborated before your task depends on it.' This clearly sets it apart from sibling tools like check_feasibility or check_physical_condition by focusing on source corroboration of an inferred fact, not on other kinds of checks.

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 gives an explicit trigger: 'Use when a step rests on something you have only inferred from text and being wrong would be expensive.' This establishes when to use the tool and implicitly tells the agent not to use it for facts that are already directly stated. It does not name alternatives among sibling tools, so it stops short of the highest score.

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