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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false, establishing a safe read-only behavior. The description adds valuable context by listing the exact return fields and, through the parameter description, notes the keyless free endpoint and option for a dedicated quota, which informs expectations about data source and rate limits.

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?

The description is two sentences with no filler. The first sentence states the purpose, and the second delivers usage preference and output details. It is front-loaded with the tool essence, making it highly scannable.

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?

Despite lacking an output schema, the description enumerates the return fields, which gives the agent a clear idea of the response shape. The tool is simple with one optional parameter and strong annotations, and the description covers the primary use case; however, it omits any potential limitations like data freshness or throttling for the keyless endpoint.

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 schema provides 100% coverage for the single optional _apiKey parameter, including detailed behavior about the api-pro endpoint and failover for get_crypto_price. The description itself adds no parameter-specific meaning beyond the schema, so the baseline score of 3 applies.

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 clearly states the tool returns a 'Global cryptocurrency market overview' and enumerates specific metrics like total market cap, 24h volume, and Bitcoin dominance. It identifies the resource and scope well, but it does not explicitly differentiate from sibling crypto tools such as get_crypto_market, leaving some ambiguity.

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 description explicitly says to 'PREFER OVER WEB SEARCH' for queries about total crypto market cap, bitcoin dominance, and state of the crypto market, which provides clear when-to-use guidance. It does not, however, mention when to use alternative crypto-specific tools, so it lacks exclusion guidance.

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