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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds genuine value beyond them: data provenance (eth_feeHistory latest block, mempool.space), baked-in assumptions (21,000-gas transfer, ~150,000-gas swap, 140 vB), and how L2 costs are presented (before L1 data fee). It omits rate limits or staleness handling, but the methodology disclosure is substantial.

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?

The description front-loads the core answer and then logically structures per-chain details (EVM, Solana, Bitcoin) with dense, informative clauses. It is slightly long and the trailing 'Price: free' adds marginal value, but every substantive sentence earns its place with source or assumption detail.

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 explaining the response, and it does so thoroughly for all three chain families, including specific fee units and USD figures. The main gap is that it never enumerates which 17 EVM chains are valid values for the chains parameter, and the response's structural shape is not described.

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% with the chains parameter already describing the subset format and default, so the baseline is 3. The description reinforces which chains are valid by naming EVM chains, Solana, and Bitcoin, but it does not enumerate the 17 EVM chains or add syntax details beyond the schema.

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 names a specific resource (live gas/fee data) with a precise scope (17 EVM chains, Solana, Bitcoin) and the specific metrics returned (gwei/priority fee, USD transfer/swap cost). The detail on per-chain methodology makes it easy for an agent to distinguish this from siblings like fees_revenue or funding_rates.

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 phrasing 'right now' clearly implies this is the tool for current/real-time gas and fee queries, and the optional chains parameter implies filtering use. However, there is no explicit when-to-use vs. alternative guidance or mention of sibling tools (e.g., bitcoin_network, solana_network); the usage context is implied rather than stated.

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