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

Annotations already cover readOnly/idempotent/openWorld/non-destructive, yet the description adds substantial context beyond them: data provenance (eth_feeHistory, mempool.space, prioritization-fee percentiles), the L2-before-L1-data-fee caveat, billing ('Price: free'), and error semantics (isError with a message, not charged). This is exactly the extra behavioral detail the annotations cannot carry.

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 purpose, then structured per chain with sourced details and a short errors/price trailer. Every sentence contributes information, though the per-chain enumeration borders on detail that could be trimmed for an agent that already sees the output schema.

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, the description need not explain return values, and it still covers sources, per-chain semantics, L2 caveats, cost and error behavior. Nothing an agent needs to invoke it 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?

There is a single optional parameter and schema description coverage is 100%, so the baseline is 3. The description contextualizes the valid chain space by naming the networks, but adds no format or syntax detail (e.g. exact accepted identifiers, default behavior) beyond what the schema already says.

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 ('what a transaction costs right now') with exact scope (17 EVM chains, Solana, Bitcoin) and enumerates the returned metrics (gwei/priority fee, USD cost of transfer and swap). An agent can distinguish this from fees_revenue, solana_network and bitcoin_network without opening any 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?

The chain coverage and per-chain breakdowns imply when the tool is appropriate (needing current, cross-chain tx cost estimates), which is clearer than most. However, it never names an alternative or states when NOT to use it (e.g. vs bitcoin_network or solana_network for chain-specific data), leaving routing to inference.

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