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

With no annotations, the description carries the burden well: it discloses the payment/metering model (x402 on Base, per-call cost), the five venues the median spans, the 50-id cap, and the shape of the payload (per-venue prices, 24h change, summed USD volume, spread %). Rate limits and failure behavior are unstated, keeping it below a 5.

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?

Four short sentences, front-loaded with the returned data, then accepted id formats, then cost. Nothing is redundant and there is no filler.

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 two-parameter, fully documented read tool with no output schema, the description supplies the missing return-value picture (per-venue prices, 24h change, volume, spread) and the payment requirement. An agent has everything needed to call it and interpret the result.

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 both `ids` and `vs` are already documented in the schema. The description restates that ids accepts CoinGecko ids or tickers plus the 50 cap, which duplicates rather than extends the schema, so baseline 3 applies.

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 states a specific verb and resource: median spot price of up to 50 coins aggregated across Binance, Coinbase, Kraken, OKX and Bybit. That scope implicitly separates it from prices_ohlcv (candles) and prices_movers, but no sibling is named explicitly, so it stops short of full differentiation.

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 gives a real usage prerequisite — $0.001 USDC per call paid via x402 on Base — which tells an agent there is a cost and payment path. However, it never says when to prefer this over prices_ohlcv or prices_movers, and gives no exclusions or error conditions.

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