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

Annotations already declare readOnly/idempotent/openWorld, so the description adds value by disclosing cost ($0.05 per call over x402), the x-credit-token prepaid header for unlimited calls, the absence of a free tier, and that no API key is needed. These are real operational behaviors an agent cannot infer from annotations.

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 question, then scope, then usage, then parameters and pricing. Dense and mostly waste-free, though the pricing/header/no-free-tier tail and 'Not financial advice' line add bulk some agents may not need.

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 an output schema present, return values needn't be explained, and the description covers purpose, use case, parameters, and cost. Complete enough to call correctly; only the lack of alternative-tool routing keeps it from a 5.

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 baseline is 3; the description goes further by stating that paymaster is required and giving the days default (30) and cap (max 90), which the schema's terse 'Lookback days (optional)' omits. It adds genuine semantics beyond the structured fields.

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 ('audits whether it's a healthy, active gas sponsor') and enumerates exactly what is measured (op volume, distinct accounts, success rate, gas sponsored, concentration). This clearly distinguishes it from siblings like gas_payer or multi_chain_gas, which address gas differently.

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?

Explicitly says when to run it: 'The read to run before integrating a paymaster... or judging who funds a counterparty's gas.' That is strong positive guidance, though it names no alternative tool or when-not-to-use condition, so it stops short of a 5.

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