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

Annotations already establish read-only, idempotent, non-destructive, open-world safety, and the description adds real behavioral context beyond that: null blocks when data is unavailable, options coverage limited to BTC/ETH, and a $0.01/call cost. It doesn't discuss latency or caching, but the disclosure of conditional availability and pricing is substantive.

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 the core claim and cost, then the field map, then the usage rule. The dense field enumeration is long but is the tool's actual value proposition; a minor trim of redundant block braces would improve it without losing information.

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 carries the full return-shape burden and does so completely: block names, key fields, nullability, symbol-conditional blocks, and price. Nothing an agent needs to decide to call this 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?

Only one parameter, symbol, and schema coverage is 100% with inline examples (BTC, ETH, SOL, HYPE). The description adds a symbol-conditional constraint (options only exist for BTC/ETH), which is meaningful semantic value the schema lacks.

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?

The description names a specific resource (one coin) and enumerates every returned block with its fields, so the agent knows exactly what this call produces. It also distinguishes itself from siblings by positioning itself as the aggregate 'full picture' call versus the 'specific 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?

It gives an explicit ordering rule: use this first for the full picture, then drill down with the specific tools. The alternatives are described only as a category ('the specific tools') rather than named, which keeps it just 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.