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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true and destructiveHint=false, so safety needs little prose. Because there is no output schema, the description carries real weight by enumerating the returned structure (base fee, tiered costs, USD per transaction type, trend, cheapest chain). It omits fetch freshness/caching behavior, which 'Current/Live' only loosely implies.

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?

A single sentence with the scope front-loaded ('Current fees on...') followed by a compact colon list of returned fields. Efficient and scannable, though the list is dense enough that it borders on a return-value dump.

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 is the only source of return-value information and it covers the main fields plus the chain coverage. Nothing critical is missing for a parameterless, read-only informational tool; only freshness/refresh semantics are left unstated.

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% and both parameters are fully described with defaults and enums in the schema itself. The description's references to 'slow/standard/fast tiers' and the named chains mirror the schema without adding syntax, defaults, or interaction details beyond it, 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?

Specific verb (returns current fees) plus concrete resource scope (five named chains) and an enumeration of returned fields, so the agent immediately knows what it gets. It stops short of differentiating from siblings such as cheapest_chain_to_deploy, which it partially overlaps by mentioning 'the cheapest chain' as an output.

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?

Read-only, always-available usage is implied by the 'Current fees' framing, and the schema makes defaulting clear. However, there is no explicit guidance on when to prefer gas_now over estimate_tx_cost for per-transaction costing, and the 'cheapest chain' output arguably encroaches on cheapest_chain_to_deploy without acknowledging it.

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