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

Annotations already declare readOnlyHint and openWorldHint, yet the description adds real value beyond them: it confirms nothing is mutated ("Reads or computes only and changes nothing"), explains why repeats are non-idempotent ("each call is charged, so repeats are not free"), and details billing mechanics (x402 USDC or card key via /credits, first 25 free, failed calls free). It also attributes the Fear & Greed data source, which no annotation conveys.

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 capability and contents, then use cases, then a concrete example, then pricing and safety notes – a sensible ordering. The pricing/payment clause is long and slightly crowds the tail, but every element (contents, cost comparison, billing, read-only guarantee) is decision-relevant for an agent.

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 compensates fully by enumerating every returned field group (sentiment index plus delta, perp price/change/funding/OI, indicator set, BTC fees) and even the data source. Cost, payment paths, free-tier behavior and the read-only guarantee are all present, leaving nothing an agent needs to call 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 param is already documented as "up to 3 coins, comma separated, default BTC,ETH,SOL". The description reinforces this by tying the coins param to the technical readings it controls and giving a concrete invocation example (coins=BTC,ETH,SOL), adding modest practical value 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?

Names a specific resource (crypto market overview) and enumerates the exact contents: Fear & Greed with 7-day change, 10 Hyperliquid perps with price/24h change/funding/OI, RSI/MACD/moving averages for up to three coins, and BTC fee rates. This clearly differentiates it from atomic siblings like crypto_fear_greed, hyperliquid_prices, hyperliquid_indicators and btc_fees that it bundles.

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?

Explicitly states intended use cases (daily market brief, trading agent context, dashboard) and positions itself versus alternatives with "Cheaper than the five tools bought one by one", so the agent knows to prefer this over individual calls. However, it never names those sibling tools, so the agent must infer which ones it replaces.

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