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

Beyond the annotations (readOnly/openWorld/non-destructive), the description discloses the paid nature: $0.002 USDC per call, billed inside the call via x402 on Base/Solana/Polygon/Arbitrum, that x402 MCP clients auto-pay, and a free sample call. This cost/payment disclosure is critical context an agent needs before invoking.

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 what it does and returns, followed by params, then pricing and a sample. Every sentence is functional, though the pricing/payment detail makes it denser than a pure read-tool blurb.

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 enumerates the returned fields, and it covers the one parameter's default behavior plus the payment prerequisite. For a single-param read tool with annotations covering safety, nothing an agent needs to call correctly is missing.

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 0% with one parameter, so the description carries the burden. It states chains is optional, defaults to all, and enumerates the supported networks in prose, compensating well for the undocumented schema, though it doesn't restate the accepted enum strings as a clean list.

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 states a specific verb+resource (current gas prices) plus the exact chains covered and the full set of returned metrics (gas price, base fee, priority fees, USD cost estimates). An agent can immediately tell this is a multi-chain EVM gas estimator, distinct from siblings like btc_fees or crypto_prices.

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?

Usage is implied rather than stated: it explains that chains is optional and defaults to all, and provides a sample input, but never says when to prefer this over btc_fees, crypto_prices, or other fee/pricing tools, nor any exclusions. Adequate but leaves selection to inference.

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