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

Goes well beyond the annotations: it discloses pricing ($0.01/call via x402 USDC or card key, first 25 free, failed calls free), which explains why idempotentHint is false — "each call is charged, so repeats are not free" turns a bare annotation flag into actionable cost behavior. It also restates the read-only nature and the fact that it accepts no required input, so the agent knows there are no side effects or prerequisites.

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?

Front-loaded with the core answer (current gas price and the three components), then usage routing, then cost/safety. Dense but every clause carries information an agent needs, though the pricing sentence is long enough to blunt the one-screen readability.

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?

There is no output schema, yet the description specifies the returned fields and their units (gwei), plus a derived figure (21k-gas transfer cost), so the agent knows what it will get. Cost, free tier, and read-only semantics cover the remaining risk for a pay-per-call read tool.

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%, so the single optional `only` projection parameter is fully documented in the schema, which sets the baseline at 3. The description adds nothing about `only` and in fact says "Takes no input," which slightly understates the tool's optional projection capability rather than enriching 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?

States a specific verb and resource — current gas price on Avalanche — and enumerates exactly what is returned (gas price, base fee, suggested priority fee in gwei, plus the cost of a 21,000-gas AVAX transfer). It also cites the underlying RPC method and names the sibling it is not (avax_receipt), so an agent can distinguish it from avax_gas_history/avax_estimate_gas without opening a schema.

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?

"Use before sending a transaction or to decide whether to wait" gives an explicit use context, and "for the fee a past transaction actually paid use avax_receipt" names an alternative with the condition that selects it. It stops short of routing against avax_gas_history (historical trend) and avax_estimate_gas (per-transaction estimate), which are the closest siblings here.

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