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

Annotations cover the safety profile (readOnly, non-destructive, openWorld), and the description adds genuinely new operational context: cost of 0.003 USDC per call, p95 latency of 1500 ms, and the shape of the returned payload. Nothing contradicts the annotations; live-and-changing fees are consistent with idempotentHint=false.

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 'Use when' trigger and one dense but efficient paragraph; exclusions follow the positive case. Minor filler ('Category: Data') and some return-detail that duplicates the output schema keep it from 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?

An output schema exists and the description still summarizes the return shape, plus it discloses pricing, latency and chain scope. Everything an agent needs to decide to call it and what to expect is present.

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 100%, so both parameters (chains, response_format) are already fully documented with defaults and enums in the schema. The description adds nothing parameter-level, so 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+resource (gas price / fee estimate) and enumerates the exact supported chains (Ethereum, Base, Solana), which lets an agent distinguish it from siblings like blackwood_token_price or blackwood_fx_rates without opening the 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?

Explicitly gives when to use (pre-transaction fee estimate, cross-chain comparison) and when not to use (gas units of a given transaction, gas history, unsupported chains). Alternatives/conditions are stated rather than inferred.

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