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

Adds substantial context beyond the annotations: cost model ($0.01/call via x402 USDC or card key, first 25 free, failed calls free), an explicit warning that repeats are charged (which explains why idempotentHint is false), the data source for USD conversion (Uniswap ETH price), and the cheapest-first sort order. Confirms read-only behavior consistent with readOnlyHint.

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-loads the resource and chains, then the returned fields, then usage and pricing — a sensible order with no filler sentences. It runs long as a single dense paragraph and includes mildly promotional phrasing ('Cheaper than the tools bought one by one'), which keeps it off a 5.

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 one optional parameter, no output schema, and annotations carrying the safety profile, the description covers what is needed: what comes back, in what order, at what cost. It stops short of naming the actual result keys an agent would receive, which matters slightly more given there is no output schema.

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?

There is one optional parameter whose schema description already covers its syntax and edge cases (unknown keys ignored, empty match returns full result) at 100% coverage. The tool description never mentions the 'only' projection parameter, so it adds no meaning beyond the schema — the baseline 3 applies.

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 prices across five named EVM chains plus Bitcoin fee rates) and enumerates the returned metrics: gas price, base fee, priority fee in gwei, transfer cost in native coin and USD, BTC sat/vB. This clearly distinguishes it from the per-chain siblings like eth_gas, base_gas, polygon_gas and btc_fees, which return data for one chain only.

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?

Gives concrete use cases — pick the cheapest chain, time a transaction, show fees in a wallet — and signals it replaces the single-chain tools with 'cheaper than the tools bought one by one.' The alternatives are referenced generically rather than named (eth_gas, btc_fees), and there is no explicit when-not-to-use clause, so it falls 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.