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

Beyond the annotations (read-only, idempotent), the description adds critical behavioral details: parallel RPC reads, unit conversion to gwei, null handling for unreachable chains, and the policy that the call is not billed if all chains fail. This substantially enriches the agent's understanding.

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 is well-organized with clear sections (supported chains, when to use, args, returns). It is appropriately detailed—every sentence adds operational value, from the parallel RPC behavior to the failure semantics.

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 fully explains the return format via an example, including a nested 'chains' array and 'source' field. It also covers error behavior and billing, making the tool's behavior clear for an agent.

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 already fully documents the 'chains' parameter (enum + description), so baseline is 3. The description adds the default behavior ('Defaults to all five supported chains') and clarifies the aggregated nature of the call, providing extra value 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 clearly states it returns current gas prices across multiple EVM chains in a single call, with a specific verb ('Reads eth_gasPrice') and resource ('multiple EVM chains'). It distinguishes itself from sibling tools by emphasizing the multi-chain aggregation and unit conversion.

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?

Explicit 'When to use' and 'When NOT to use' sections give concrete use cases (cheapest chain selection, cost estimation, low-gas monitoring) and exclusions (EIP-1559 breakdown, historical data). This provides clear guidance for tool selection.

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