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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety bar is low. The description does add genuinely useful context beyond them: per-call pricing of $0.03 USDC/credits and the fact that payment travels in MCP headers (X-Payment / X-Payment-Tx / Bearer fg_…) rather than params, which is a real invocation constraint. However, it never says what a 'window' is, what unit days is in, or what happens when days is omitted, leaving the core read behavior underspecified.

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 purpose is front-loaded and the metric list is efficient, but the payment information is repeated three times across the Chinese and English blocks, and the header sentence duplicates what the [zh]/[en] lines already say. Substantial trimming is possible without losing content.

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 one optional parameter, no output schema, and annotations covering the safety profile, the definition covers the essentials: what it returns, what it costs, and how to pay. Missing are the semantics of the days window (units, default, max) and any hint at response shape, which matter for correctly invoking a time-windowed data tool.

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 0% and the sole parameter 'days' has a null default with no type-level meaning. The description only says '参数 days 可选' / 'Args: days', effectively restating the schema's optionality without giving units, a sensible range, or the default window used when it is omitted. That is a clear gap where the description should have compensated for the undocumented parameter.

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 names a concrete resource and enumerates the exact payload: six window metrics (transactions, active addresses, miner revenue, fees) plus hashrate and price. 'Full' versus the sibling btc-onchain.btc_activity is implied by the wording but never stated outright, so an agent must infer the distinction from the name rather than the text.

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?

Usage is only implied: an agent gathers that 'full' means the complete six-metric set and that this is the paid $0.03 tier. There is no explicit 'use this when you need all metrics, use btc_activity for a cheaper subset' routing statement, and no exclusions or prerequisites are given.

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