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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial context on top: per-call pricing ($0.002, 10 free/day, x402 payment-required results), error behavior (isError with a message, not charged on failure), and the computed stats returned. This is well beyond what the annotations provide.

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 the tool returns, then usage, then price, then errors — a sensible ordering with no filler sentences. The server URL and payment detail make it slightly dense, but every clause carries actionable information.

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?

For a priced, analytics-returning read tool with four params, an existing output schema, and full annotation coverage, the description supplies everything an agent needs: scope, sibling routing, cost, failure semantics, and return-shape summary. Nothing material 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?

Schema description coverage is 100%, so the baseline is 3 and the schema already documents days, asset, chain and interval. The description adds the 'same asset resolution as crypto_price' hint, but it also introduces a conflict: it claims hourly points up to 90 days while the schema states hourly is allowed only up to 30 days.

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+resource (historical USD prices for any crypto asset) with the returned analytics enumerated (return, high/low, max drawdown, annualized volatility), and explicitly separates itself from the sibling crypto_price. An agent can distinguish it from every other tool in the list without opening a schema.

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?

Contains an explicit 'When to use' clause covering past prices/drawdowns, names the alternative tool (crypto_price) for current price, and even gives the alternative's server URL. Exclusions are stated, not inferred.

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