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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds valuable context by stating it 'reads live data directly from the market data feed' and 'No AI cost', and explains the meaning and freshness of returned fields. This goes beyond the annotations without contradicting them.

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 well-structured: a concise opening sentence followed by a clear bulleted list of return fields. Every sentence adds value, avoids redundancy, and the format makes it easy to scan.

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?

Given this is a zero-parameter tool, the description comprehensively explains the output fields, including their meanings. With an output schema present, the description fully covers what an agent needs to know to invoke and interpret the 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?

The tool has zero parameters, so schema coverage is 100% by definition. With no parameters to document, the description is not required to add parameter details; the baseline score of 4 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?

Description clearly states it provides a 'Live market health snapshot in a single call' and enumerates the aggregated indicators (VIX, fear/greed, breadth, indices, bonds). This goes beyond the name by specifying the resource and scope, and differentiates it from sibling tools by emphasizing that it aggregates data without requiring multiple calls.

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 implies the tool is for quickly obtaining a market-wide health overview in one call, and notes 'No AI cost' and 'Available to all tiers', which are useful usage considerations. It does not explicitly list exclusions or name alternative tools for when more detail is needed, but the single-call aggregation message provides clear context.

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