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

With no annotations, the description carries the full burden. It usefully discloses the cost/freshness tradeoff and where the paid variant lives, which is real behavioral context. It omits key traits for a freshness-tiered tool: how stale 'cached' data may be, rate limits on the free path, and whether results differ in shape between tiers.

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, front-loaded with the data served and the tiering model. The trailing sentence about the paid endpoint is promotional but does convey a genuine usage channel, so it earns partial keep; a small amount of framing could be trimmed.

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?

For a single-parameter, no-output-schema read tool with full schema coverage, the description covers what is returned, the two modes, and the cost model. The remaining gap is the absence of any indication of freshness windows or response shape, which would matter for the 'cached' mode.

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 enum already documents the two values, so a 3 baseline applies. The description goes slightly beyond the schema by attaching meaning to each tier ('cheap' vs 'guaranteed current'), which helps the agent choose a value rather than just enumerate it.

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?

It names the resource (gas + ETH/USD data) and the defining dimension (freshness tier), which is more specific than a generic 'get data'. It does not, however, contrast itself against the many siblings that also serve gas or ETH price data (get_gas_metrics, get_reliable_eth_price, get_normalized_gas), so an agent still has to infer which source to pick.

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 tier hints ('cached (cheap)' vs 'live (guaranteed current)') imply when each option is appropriate, and the pay-per-call note signals a production context. But there is no explicit routing guidance versus sibling tools, and no statement of when this tool should not be used or what limits apply to the free MCP path.

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