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

The annotations already declare readOnlyHint=true and openWorldHint=true, so the description's added value is the payment and charging behavior: the answer is checked first, failures are not charged, and a call costs 0.013714 USDC via x402 on Base. That is useful context beyond the annotations, but it does not explain answer validation, latency, or data freshness.

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?

The description is short and front-loaded, with no filler beyond the core payment terms. Its main weakness is that the opening sentence is vague rather than purpose-driven, but the structure itself is efficient.

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 paid query tool with four parameters and no output schema, the definition is incomplete. It covers charging mechanics but omits what question types exist, how pool and block are used, what is returned, and why chainId is limited to 8453.

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?

The description does not explain the meaning of question, chainId, pool, or block. With only 50% schema description coverage and some confusing schema mappings (pool described as pool_tokens, block as block_hash), the description fails to compensate for the gap.

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 says it returns "One data.onchain_query answer, bought through Moonbeam," which mostly restates the tool name/title. It does not clearly explain that it queries specific onchain data such as pool tokens or block hashes, even though the schema enums reveal those use cases.

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 no guidance on when to use this tool versus siblings like market_price, risk_address, or mcp_digest. The payment details are operationally useful but do not help the agent choose between tools or decide when this query is appropriate.

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