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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description goes well beyond them by disclosing the cost model ($0.002 USDC per successful call), the payment mechanism (x402 on Base, Solana or Arc), and the failure-billing rule (failed calls are not charged) — exactly the operational context an agent needs before spending money.

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 sentences, zero filler: the first front-loads what the tool returns and its source, the second front-loads the billing consequence. Both sentences earn their 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?

An output schema exists, so the return shape need not be spelled out, yet the description still enumerates the key fields. With cost, payment rail, failure billing and endpoint all covered, nothing material an agent needs to call this correctly is missing.

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%: the schema already documents the comma-separated, t-prefixed Bitfinex v2 symbol format and the cap of 10. The description's example (tBTCUSD,tETHUSD) mirrors the schema example and adds no new syntax or constraint beyond it, so the 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?

Specific verb+resource: Bitfinex spot ticker for one or more pairs, with the exact fields returned (bid, ask, last, 24h change, volume) and the named upstream endpoint (public v2 ticker). It cleanly separates itself from the many sibling exchange-ticker tools by being explicitly Bitfinex-scoped.

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 clear context for use: when you need Bitfinex spot ticker data for specific pairs, with the symbol convention stated. It does not explicitly name alternatives (e.g. finance_bitstamp_tickers, finance_binance_prices) or state when-not to use it, so it stops short of a 5.

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