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

Annotations already declare readOnly/openWorld/destructive=false, and the description still adds material behavior the agent cannot see elsewhere: a per-call price ($0.001 USDC via x402 on Base), the errors-are-free guarantee, a 5 s cache, sub-500 ms typical latency, and that values come from public Base RPC. Cost and cache semantics are exactly the kind of context that changes invocation decisions.

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 most decision-relevant facts (what it is, chain, cost) and dense with substance rather than filler. It loses a point for redundancy — the free-on-error guarantee appears in both the opening bracket and the closing sentence — and for the promotional upsell appended to the tail.

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 (payload fields, derived `summary`, `baseFeeTrend`, `congestion`), plus freshness, caching, latency, and cost. Nothing an agent needs to call this correctly or interpret the response is absent.

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?

Zero parameters, so the baseline is 4; the description reinforces this with an explicit "No params," which removes any ambiguity about whether filters (block range, percentile) are accepted. Nothing further is needed.

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 — a live gas snapshot for Base mainnet (chain 8453) — and enumerates exactly what is read (block number/time/utilization, base fee, gasPrice, priority fee, 10-block history, percentile suggestions, cost estimates in ETH and USD). It also separates itself from the sibling base_snapshot by naming that tool's broader scope (ETH price + network health). An agent can route without opening any 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?

The use case is clear and a concrete alternative is offered with a selecting condition: "Need ETH price + network health too? /api/base/snapshot ($0.003)." What's missing is an explicit statement of *when not* to call this (e.g. for historical gas or for non-Base chains), so it lands at clear-context rather than full when/when-not coverage.

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