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

Annotations already mark it read-only and open-world, so the description does not need to restate safety. It adds valuable non-annotation context: the public md/v2 endpoint, the cost of $0.002 USDC per successful call via x402, and the fact that failed calls are not charged.

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 sentences, with the core purpose and returned fields front-loaded before the pricing and endpoint details. Every sentence adds useful information without repetition.

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 one required parameter, a full schema description, annotations, and an output schema, the description supplies everything needed for correct invocation. It also covers cost, endpoint, and failure charging, which are not captured by the structured fields.

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% for the single symbol parameter, so the schema already carries the parameter semantics. The description repeats an example symbol but does not add format or validation details beyond the schema, making the baseline 3 appropriate.

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 states a specific verb/resource combination: a Phemex perpetual-contract ticker for one symbol. It enumerates the returned fields and names the exact endpoint, and the Phemex exchange qualifier distinguishes it from the many sibling exchange ticker 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?

The 'for one symbol' phrasing implies usage for single-symbol lookups, but there is no explicit when-to-use guidance relative to the numerous sibling exchange tickers (Binance, Bitget, MEXC, etc.). An agent must infer that this is the Phemex-specific alternative.

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