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

Annotations already cover the read-only and open-world profile, but the description adds genuinely useful behavioral context: the data window (last 20 blocks) and, notably, the paid cost model ($0.0001 via x402), which signals a payment requirement an agent would not otherwise anticipate. Return format and rate limits remain unspecified.

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?

Purpose is front-loaded in the opening clause, and the dense semicolon lists map directly to returned fields, so most tokens earn their place. It is on the long side, but the enumeration is informative rather than padding.

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 burden of describing returns, and it does so thoroughly (fee tiers, cost estimates, congestion, block metrics, Solana specifics). The only meaningful gap is the absence of when-to-use guidance relative to sibling tools.

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 description coverage is 100%, so both parameters (usd, chains) are already documented, including the full chain enum list. The description restates the chain set but adds no syntax or default nuance beyond the schema. Baseline 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?

The description names a specific verb+resource (real-time gas fees and network health) and enumerates the exact chains and metrics covered, down to EIP-1559 tiers and Solana priority-fee percentiles. An agent can immediately distinguish this from siblings like crypto_prices, swap_route, or simulate_tx.

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 is rich on what the tool returns but silent on when to choose it over siblings. There is no explicit 'use this when' guidance or exclusions (e.g., against crypto_prices for token prices), so selection is left to inference from the metric list.

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