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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds useful behavioral context: the $0.001 USDC cost, the byte-identical equivalence to a specific GET endpoint, and the conditional presence of fees and pool name depending on explorer attachment.

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?

Two sentences with no filler. The core return fields are front-loaded, followed by cost and endpoint equivalence. Every sentence earns its place.

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 simple read-only list tool with an output schema and safety annotations, the description is nearly complete. It covers cost, source, fields, and endpoint equivalence. It does not explain when to prefer this over siblings, but that gap is already accounted for in usage_guidelines.

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 'limit' parameter is already described with default and endpoint behavior. The description adds no further parameter semantics beyond the endpoint example with limit=20, which may even slightly conflict with the schema's default of 10. Baseline 3 is appropriate.

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 identifies the resource as recently indexed Bitcoin blocks and enumerates the fields returned, which distinguishes it from sibling tools like market_btc_chain_tip or market_btc_network_stats. It lacks an explicit verb like 'list' or 'fetch', but the meaning is unambiguous.

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 implies usage: call this tool when you need the latest Bitcoin blocks indexed by the explorer. It does not explicitly contrast with alternatives or state when not to use it, but the byte-identical endpoint mapping and cost note provide some practical context.

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