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

Goes well beyond the read-only/idempotent annotations: it explains the ranking rationale (abnormality vs the coin's own usual 8-hour move), discloses partial-failure behavior (a stale source is dropped and named), the 503-without-sampler path, billing semantics ('never billed'), and the exact price and payment rails. This is unusually complete behavioral context for a paid aggregation tool.

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 the trigger condition and scoped in three sentences with no filler. The long middle enumeration of returned items is dense but every element is a distinct signal the agent may care about, so it earns its place even though it borders on packing too much into one sentence.

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?

An output schema exists, so return-field definitions are not the description's burden, yet it still characterizes the content and ordering of the response. Cost, payment mechanism, partial-data handling and failure mode are all covered, leaving nothing an agent needs before calling.

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 no parameter semantics to document; the baseline for a no-param tool is applied. The description correctly avoids inventing inputs and instead pins down coverage (four named assets, fixed 8-hour window).

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?

States a specific verb (summary/one-answer) with an explicit resource scope: last 8 hours across BTC, ETH, SOL and HYPE. That aggregate framing distinguishes it from single-metric siblings like get_signal_board, get_funding_pulse or get_market_snapshot without needing to name them.

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?

Opens with an explicit trigger, 'Use when an agent needs a one-answer summary of the last 8 hours', which gives a clear selection condition. It stops short of naming when NOT to use it or which specific sibling to prefer for a single-metric question, so it earns a 4 rather than a 5.

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