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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful context about units and decimal precision and includes the underlying REST operation, but does not mention response shape, pagination, or caching behavior.

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: the first sentence states exactly what is returned, followed by a docs link and the REST endpoint. Every sentence earns its place, though the REST line is somewhat redundant for an agent that only needs the call semantics.

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 single-parameter read tool with annotations covering safety and an output schema covering return values, the description is adequate. The main missing piece is sibling differentiation against get_block_fee_rates and get_precise_fees, which matters given the dense list of similarly named tools.

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%, and the single time_period parameter is fully documented in the schema with enum values and examples. The description only says 'for a time period' and adds no syntax or format details beyond what the schema already provides, so 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 states a specific verb and resource ('Get block fee rate percentiles') and enumerates the exact percentiles returned plus units (sat/vB, 3 decimals). This is more specific than the sibling get_block_fee_rates, but it does not explicitly state how it differs from that sibling or from get_precise_fees.

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?

There is no guidance on when to use this tool versus the closely named siblings get_block_fee_rates or get_precise_fees. The 'precise' qualifier implies a distinction, but the description never states it or gives any exclusions.

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