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

With no annotations, the description carries the full burden and delivers important behavioral detail: it is a paid call ($0.005) via x402 on USDC Base, which tells the agent a payment flow is required, and it enumerates the returned data points and value scale. It omits rate limits and failure behavior, but the cost/auth disclosure is genuinely useful context beyond what structured fields provide.

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 compact segments with the cost and payment rail front-loaded before the resource. Every clause earns its place, though the parenthetical payment detail slightly interrupts the flow.

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 simple no-parameter, no-output-schema read tool, the description covers cost, payment mechanism, and the exact return values (including the sentiment scale), which is what an agent needs to call it correctly. It stops short of explaining freshness/caching or error handling, but nothing essential 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?

The tool takes zero parameters, so the baseline is 4. The description correctly implies no inputs are needed by framing the call as a direct fetch.

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?

States a specific verb and resource ('crypto Fear & Greed index') plus the exact data it returns (today, yesterday, week ago, 10-day history) and the 0-100 scale. It is distinguishable from siblings like get_market_pulse or get_crypto_price by its unique sentiment resource, though it does not explicitly name what separates it from those other market-signal tools.

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?

'Market sentiment signal for trading agents' implies the context in which to use it, but there is no explicit when-to-use vs when-not, no prerequisites, and no mention of alternatives such as get_market_pulse. Usage is suggested rather than specified.

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