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

Beyond the read-only/idempotent annotations, it discloses refresh cadence ('Refreshed daily'), a real history limitation ('history is month-end only'), and that history is 'computed point-in-time from that date's top-50 ranking' — exactly the kind of caveat an agent needs to avoid misreading the series.

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-loads the metric definition, then usage, then cadence caveats. The definition sentence is dense due to the nested parenthetical, but every clause (scale, exclusions, lookback, thresholds) carries meaning.

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 parameters, no output schema, and safety already covered by annotations, the description fully supplies the remaining burden: what the index means, what accompanying values are returned, how fresh the data is, and the history granularity.

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 no parameters, so there is nothing for the description to disambiguate. Baseline for a zero-parameter tool is 4.

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?

Names a specific resource (Altcoin Season Index) and gives its exact scale, computation basis, exclusion rules, and thresholds. The verb/resource pairing plus the sibling set (ETF flows, cycle indicators, market snapshot) makes the scope unmistakable.

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?

Explicitly states when to invoke it: 'Use this when the user asks whether it is altcoin season or how altcoins are performing against Bitcoin.' No alternatives or when-not-to-use cases are named, but the trigger conditions are clear.

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