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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the bar is lower. The description adds valuable context: the per-call cost, the approximate horizon (~8 blocks), the specific fields returned, and byte-identity to a known REST endpoint. 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?

Two tight sentences deliver the core purpose, return contents, cost, and endpoint equivalence without filler. The most important information is front-loaded and every clause 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?

With an output schema present, rich annotations, and only one optional parameter, the description covers the essential operational details: what is returned, the cost, and the exact REST equivalent. Nothing critical is missing for an agent to invoke it 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 coverage is 100%, and the single 'limit' parameter is already described in the schema. The description adds the '~8 blocks' context and the REST endpoint's limit=20, but does not materially expand on the parameter's meaning or formatting beyond the schema.

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 resource (per-block projections for the mempool's next ~8 blocks) and enumerates the returned fields (size, transaction count, total fees, median fee, fee-rate range). It does not explicitly contrast itself with sibling tools like market_btc_fee_estimates, but the specific scope 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 gives a usage-relevant cost warning and notes byte-identity to a REST endpoint, but it provides no guidance on when to choose this tool over alternatives such as market_btc_fee_estimates or market_btc_recent_blocks. No when-to-use or when-not-to-use context is offered.

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