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

The description discloses the data source (CoinGecko), the exact time windows (30/90/365), and the cost ($0.15 USDC via x402), all of which go beyond the readOnlyHint, openWorldHint, and idempotentHint annotations. No contradiction with annotations.

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?

Three concise, front-loaded sentences: the first states the core function, the second gives use cases, and the third provides source and pricing. Every sentence earns its place with no redundancy or fluff.

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 tool is simple (2 params, enums, output schema exists) and annotations cover safety. The description adds essential missing context: source, cost, and use cases. It fully equips an agent to invoke the tool correctly.

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% with enums and descriptions for both coin and days. The description mentions the days windows but does not add extra semantics beyond what the schema already provides. Baseline of 3 is appropriate when the schema does the heavy lifting.

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 clearly states the tool returns historical daily closing prices for supported cryptocurrencies over 30, 90, or 365 days. The verb 'Returns' plus the resource 'historical daily closing prices' makes the purpose unambiguous and distinguishes it from siblings like get_crypto_price.

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?

The description explicitly says 'Use for trend analysis, drawdown calculation, or training data,' which provides clear when-to-use guidance. It does not name alternative tools or state when not to use it, but the use cases are sufficient for an agent to select it appropriately.

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