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

With no annotations, the description carries the full behavioral burden, but it does disclose genuinely useful context that structured fields don't: the tool is paid (0.01 USDC on Base via x402, or 12 sats Cashu/L402) and sourced from mempool.space. It says nothing about data freshness, caching, rate limits, or response latency, which matters for a stats endpoint.

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?

Front-loaded with the metrics the tool returns, followed by the payment options in a single tight sentence. Every clause earns its place; only the payment enumeration is slightly bulky.

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 one-parameter read tool with no output schema, the description effectively substitutes for a return-value spec by listing the metrics, and it flags the payment requirement. Nothing essential to invoking it correctly is missing, though the default unit and freshness remain unstated.

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%, so the description must compensate, and it does: it documents the single parameter's accepted values (btc|sats) and scopes it to capacity only. This is meaningfully more than the bare schema provides, though it doesn't state the default unit.

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 specific resource (Bitcoin Lightning Network statistics) and enumerates exactly which metrics are returned: channel and node counts, total capacity, average/median fees and channel sizes. It also names the data source (mempool.space). It does not explicitly differentiate itself from siblings like btc_snapshot or crypto, which is the only thing keeping it from a 5.

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 explicit when-to-use or when-not-to-use guidance, nor any mention of the sibling tools (btc_snapshot, crypto) that an agent might confuse this with. Usage is only weakly implied by the resource name, so the agent has to infer the routing decision itself.

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