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

Annotations already declare read-only, idempotent, non-destructive, so safety is covered. The description adds useful context ($0.01 cost and the GET route), but the 402 payment/retry behavior — the genuinely tricky part — lives only in the schema, not the description.

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 terse fragments, zero waste, return scope front-loaded before the endpoint and price. Slightly telegraphic style but appropriately sized for a trivial no-arg read.

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?

No output schema exists, and the description does state what comes back (index + 7-day history). Combined with annotations and a fully documented payment param, an agent has enough to call it correctly; only the challenge/retry loop is left implicit.

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 optional 'payment' param is fully documented there. 'No params' adds a small confirmation but arguably undersells the optional payment mechanism that the schema describes at length.

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 resource (Crypto Fear & Greed Index) plus explicit return scope (7-day history), pinned to a concrete route. An agent can distinguish it from siblings like get_crypto_prices or get_btc_fees without inspecting other schemas.

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?

States 'No params' and the cost, implying a direct fetch, but never says when to prefer this over get_crypto_prices or any other market-sentiment sibling, nor any exclusions.

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