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

With no annotations, the description carries the full burden and does well: it discloses a 60-second cache, the underlying provider (CoinGecko), and an x402 paid-access cost of $0.02/call (USDC on eip155:8453). It omits failure behavior and whether tickers are resolved client- or server-side, but the freshness and payment characteristics are valuable context.

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 core function and stays compact, but the 'Use this when an agent needs...' sentence is redundant with the opening sentence and could be merged with it. The x402 pricing sentence earns its place as actionable cost 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 2-param read tool with no output schema and no annotations, the description covers source, accepted inputs, returned fields, cache freshness, and cost. Only the exact response shape (e.g., object structure) is left unstated, which is a minor gap given there is no output schema.

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%, so the baseline is 3. The description adds meaning beyond the schema's terse 'Coin ids or tickers' by giving concrete ticker examples (btc, eth, sol…) and clarifying that both ids and tickers are accepted, which reduces ambiguity about the ids parameter.

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 names a specific verb+resource (live cryptocurrency prices), the data source (CoinGecko's public API), the exact outputs (current price in USD/EUR/GBP/JPY plus 24-hour change), and accepted input forms (coin id or common ticker). This makes it immediately distinguishable from sibling tools like crypto_gas_price or crypto_stablecoin_metrics, which cover different crypto data.

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 provides a 'Use this when an agent needs live token prices and 24h change' sentence, but that largely restates the purpose already stated. No alternatives are named (e.g., live_exchange_rates for fiat) and no exclusions are given, so guidance is only implied rather than routing.

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