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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: hourly-close granularity regardless of chart interval, the 31-day ceiling, percentile comparison against prior observations of the same market, the 4h/1d/7d separation rule, and the caveat that null ranks can mean building history. The USDC/USD proxy note is precisely the kind of hidden behavior an agent could not infer.

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?

It is front-loaded with the use-case trigger and then cleanly partitioned into Selection/Presentation/Evidence blocks, so each section is scannable. It is denser than necessary for a two-parameter tool, with some sentences carrying multiple instructions, but little is pure 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?

With an output schema present, annotations covering the safety profile, and full schema description coverage, the description only needs to add interpretation guidance. It does so: which evidence fields to read first, what null ranks imply, and how to preserve USD/USDC identity.

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%, so the schema already documents ticker format and the inclusive-start/exclusive-end window semantics in detail. The description only echoes the resolved-ticker and timezone-qualified-window guidance and adds no format or edge-case detail the schema lacks, 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 and resource ('Read hourly market regime and volatility') and scopes it to a user intent ('changing volatility or how unusual its volatility is within its own history'). It distinguishes itself from non-tools via exclusions, but never differentiates from the near-identically-named sibling research_show_market_context, leaving that potential confusion unresolved.

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 'Use this when...' trigger plus a strong 'Do not use for...' list covering price predictions, trading decisions, calibrated confidence, annualised volatility and the retired regime archive. The one gap is that exclusions are stated as task categories rather than routing to a named alternative sibling tool.

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