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

With no annotations, the description carries the burden. It usefully discloses the $0.01 x402 cost and the spot/historical nature of the data. However, it does not describe response shape, error behavior, rate limits, or whether this is a safe read-only operation.

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?

One dense sentence covers cost, data type, identifier formats, and examples. Every element earns its place and the most important caveat ('Prefer ?coins=') is placed at the end as a recommendation.

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?

The description is sufficient for a straightforward price lookup but leaves gaps: no output schema, no annotations, no explanation of how to request historical vs spot data via the 'at' parameter, and no mention of the response format.

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 high, but the description adds real value by clarifying that 'coins' is preferred and supports tickers or chain:address formats, while 'ids' is legacy CoinGecko IDs. This goes beyond the schema's terse examples, though x_payment remains unexplained.

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?

Description clearly states a specific function: retrieving spot or historical USD prices. It distinguishes from crypto sibling tools by specifying identifiers (ticker, CoinGecko id, chain:address) and giving concrete examples (BTC, ETH, bitcoin, base:0x…).

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?

No explicit guidance on when to use this tool instead of siblings like crypto_market_metrics, dex_token_data, or get_crypto_liquidations. 'Prefer ?coins=' is parameter guidance, not alternative selection guidance.

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