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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds value by disclosing the $0.001 USDC cost, which is not captured in annotations or schema, and 'Fetches' is consistent with the read-only annotation.

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?

A single, front-loaded sentence conveys the core purpose and cost with no wasted words. Every element earns its place, and the cost detail is cleanly appended in parentheses without distracting from the main function.

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?

This is a simple, zero-required-parameter read-only tool with a complete schema, helpful annotations, an output schema, and a clear one-sentence description. Nothing essential is missing for an agent to invoke it correctly.

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?

There is only one optional parameter and schema description coverage is 100%, so the schema already fully explains includeLatency. The tool description adds no additional parameter meaning beyond what the schema provides, so the baseline score of 3 is 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?

Description names a specific verb ('Fetches'), a specific resource ('Arc Mainnet'), and concrete outputs ('block height, gas fees, and node metrics'), plus cost. This clearly differentiates it from broader analytics siblings like base_analytics and from deployment tools like deploy_arc_contract.

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 implies the natural use case: when an agent needs Arc Mainnet block height, gas fees, or node metrics. It does not explicitly mention alternatives or exclusions, but the target context is clear enough for straightforward selection among the sibling tools.

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