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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description correctly focuses on what annotations can't convey: the mandatory payment of 0.005 USDC via x402 or API-key auth, and the fact that an x402-capable client auto-pays. That is genuinely decision-relevant. It doesn't state freshness/update cadence of the

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 short blocks, both front-loaded: the snapshot contents come first, then the usage condition, then the access/payment note. No sentence is filler, and the bracketed pricing note earns its space because it changes whether an agent's call will succeed.

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 input schema, no output schema and no annotations beyond safety hints, the description carries the full burden and meets it: it lists the return contents and discloses both auth paths and cost. An agent knows what it will get, what it will pay, and when to prefer this over per-asset tools.

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?

The tool takes zero parameters, so the baseline is 4 and there is nothing for the description to disambiguate. The description appropriately spends its words on scope and cost instead of inventing parameter commentary.

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 (global crypto market snapshot) and enumerates exactly what it returns: total market cap, BTC dominance, 24h volume and 24h change. The final clause explicitly contrasts it with a per-asset reading, which separates it from the many per-token siblings like get_asset or get_ohlcv.

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?

Gives a clear trigger condition: the user asks about overall market conditions or wants a macro view. It also excludes the per-asset case. It stops short of naming the specific alternative tools (get_market_data, get_market_regime, get_benchmark) that overlap most with a macro snapshot, leaving some routing ambiguity.

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