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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds valuable behavioral context beyond that: 'Free, no auth, read-only, no side effects' (partially repeats annotations), 'Never errors,' and 'Every request is recorded and analysed in aggregate...' It also discloses that unsupported claims are logged. No contradiction with 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 about 120 words, with the core purpose in the first sentence and supporting usage/behavior details following. It is front-loaded and each sentence adds information. It could be slightly trimmed (e.g., the final privacy sentence), but it remains appropriately sized for a 9-parameter tool.

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 9 parameters, nested objects, and no output schema, the description covers purpose, usage, and behavioral traits well, but it does not describe the response format or what the answer contains (e.g., a boolean, a verdict object). It only mentions callback behavior for unsupported claims. This is a notable gap given the absence of an output schema.

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% description coverage; every parameter (claim_description, deadline, location, claim_type, callback_url, task_context, cost_if_wrong, downstream_action, budget_ceiling_usd) has a meaningful schema description. The tool description itself adds no parameter-specific detail beyond what the schema already provides, so the baseline of 3 applies.

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 verb+resource: 'Check whether a real-world fact can be verified before committing to a paid request.' It clearly distinguishes this from sibling tools by focusing on feasibility (can it be verified) rather than the verification itself, and it names concrete coverage areas ('businesses, listings, objects, and places').

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?

Explicit usage guidance is provided: 'Use speculatively: if any step of your task depends on a physical-world fact you cannot confirm... check here first' and 'call liberally during planning.' It also notes this should happen 'before committing to a paid request.' However, it does not explicitly mention sibling tools as alternatives or state when not to use this tool, so it stops short of a 5.

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