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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so safety is covered; the description adds that it performs live fetching of mempool and fee data and returns a machine-actionable verdict plus pressure level and savings estimate. It omits one material behavior: this is a paid endpoint whose first call returns a Lightning invoice rather than a verdict, which an agent only discovers from the schema.

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?

Three sentences, front-loaded with the outcome and followed by mechanics and fit, so an agent gets the gist from the first line. Minor redundancy between "composited send-or-wait recommendation" and "machine-actionable verdict" keeps it off a 5.

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 no output schema, the description does the necessary work of naming the return fields (verdict, sat/vB fee rates, mempool pressure, estimated savings), which is the key gap it had to fill. The missing piece is the pay-per-call gating on the first invocation, though that is recoverable from the schema.

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 enum for urgency plus the L402 proof flow are fully documented there, so the schema carries the parameter burden. The description adds no meaning beyond it, not even referencing urgency as the lever that shapes the verdict, so baseline 3 applies.

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?

"Returns a composited send-or-wait recommendation for a Bitcoin transaction" names a specific verb and artifact, and the enumeration of verdicts (SEND_NOW, WAIT, URGENT_ONLY) pins down exactly what comes back. An agent can distinguish this from btc_price or optimal_send_window without opening the schema.

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?

"Ideal for agents that need a single decision call instead of parsing multiple raw mempool endpoints" gives a clear situational fit. However, it never names or excludes the closest sibling, optimal_send_window, which plausibly overlaps in intent, and gives no when-not-to-use condition.

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