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

Annotations only cover readOnlyHint and openWorldHint, and the description adds genuinely non-obvious behavior: the data comes from an undocumented JSON endpoint that can change without notice. It also discloses the paid-call model ($0.002 USDC per successful call via x402 on Base, Solana or Arc) and, importantly, that failed calls are not charged.

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 source caveat, alternatives, and price — a sensible priority order with no filler sentences. Slightly dense as a single run-on block, and the B-Stock aside is the weakest link in the chain.

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?

A one-parameter read tool with an output schema, so return-shape documentation is not required, yet the description still names the fields. Source volatility, cost model, failure charging, and sibling routing are all covered — nothing an agent needs in order to call it correctly 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 coverage is 100% and already documents the limit range and default of 10, so most of the burden is carried there. The description still adds the semantic that the limit is a rank cutoff ("top N coins"), which matters because it tells the agent results are ordered by market-cap rank rather than arbitrarily sampled.

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 resource and enumerates the exact fields returned (name, symbol, USD price, market cap, 24h volume, 24h change) scoped to the top-N ranked coins, which is far more specific than the title alone. It differentiates from finance_coingecko and finance_bstock by name. The one gap is that the much closer sibling crypto_coinmarketcap_listings is never mentioned, so an agent comparing those two gets no help.

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?

Gives explicit routing conditions for two alternatives ("finance_coingecko when you need CoinGecko spot prices for up to 10 coins in one currency", "finance_bstock when you need B-Stock wholesale liquidation auctions"), which helps eliminate wrong selections. It stops short of stating exclusions for this tool itself, such as historical prices or per-coin detail beyond the top-100 cutoff.

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