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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false), so the description's job is added semantics — and it delivers the critical non-obvious fact that this is a RISK score where LOWER IS HEALTHIER and a rising value means deterioration, plus the numeric band mapping. That prevents a plausible misinterpretation the annotations cannot address.

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?

Front-loaded with what is returned, then the essential interpretation rules, then the sibling pointer. The regime band enumeration is four clauses that consume space but carry genuine interpretation value, so it is justified rather than padding.

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?

There is no output schema, so the description carries the burden of describing the return shape, and it does so explicitly (final score, regime label, three layer scores). For a zero-argument read tool with full annotation coverage, nothing an agent needs to call and interpret it is missing.

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 takes zero parameters, so there is nothing for the description to disambiguate; baseline for a parameterless tool is 4. The description correctly avoids inventing any argument guidance.

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 names a specific resource (today's Zensei Index for U.S. equities) and enumerates exactly what the tool returns: the final score, its regime label, and three layer scores. It is clearly distinguishable from siblings, which are about/about-summary/indicator-drilldown rather than the headline daily reading.

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 routes the agent explicitly to zensei_index_indicators for causal drill-down ('Call zensei_index_indicators to see why the score sits where it does'). It does not, however, state when to prefer this over zensei_index_summary or zensei_index_about, so the sibling disambiguation is partial rather than complete.

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