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

Annotations already flag read-only and open-world, and the description layers on the things annotations cannot express: a $0.002 USDC cost per successful call, x402 payment rails (Base, Solana, Arc), and that failed calls are not charged. It also attributes values to Blockchair as the reporting source.

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?

Purpose is front-loaded in the first clause, followed by the metrics and then a compact pricing sentence. The eight-chain enumeration is duplicated from the schema, which is mild waste but helps a scanning agent.

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?

Return values are partly described and an output schema exists, so return shape need not be spelled out. For a single-optional-param read tool, the description covers data scope, supported inputs, and cost/payment obligations.

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% and the single parameter already documents the allowed values and the bitcoin default, so the description adds little beyond restating the chain list. Baseline 3 applies when the schema carries parameter meaning.

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?

States a specific verb and resource ('Blockchair chain statistics for one blockchain') and enumerates the metrics returned: block/transaction counts, mempool size and fees, hashrate, volume and USD price. The named upstream source plus multichain scope separates it from the one other chain-stats sibling (dev_gmx_arbitrum_stats).

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 phrase 'for one blockchain' plus the enumerated chain list and default make the call pattern clear (one chain per call, bitcoin if unspecified). There is no explicit when-to-use/when-not guidance versus alternatives, so it stops short of a 5.

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