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

Annotations already declare idempotentHint=true and openWorldHint=true, but the description adds material facts the schema does not: the exact cost (0.002500 test USDC), the settlement network (eip155:84532), and the requirement to reuse the idempotency key only for retries. The paid, non-read-only nature of the call is disclosed even though readOnlyHint=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?

Three short sentences, front-loaded with the operation, then cost, then retry handling. Every sentence carries information; nothing is padded.

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 should carry the return shape but only says 'Read eth_chainId' without noting it returns a hex-encoded chain id. The payment and idempotency context is strong, but the result contract is left implicit for a two-required-param paid tool.

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 50%: idempotencyKey is well documented in the schema, while the empty params array is undocumented anywhere. The description reinforces the idempotencyKey retry semantics but does not clarify that params must be an empty array for this RPC.

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 and resource: 'Read eth_chainId from Ethereum (eip155:1)', with the chain namespace disambiguating it from the bitcoin_* siblings and the other ethereum_* RPC methods. It does not explicitly contrast itself against named alternatives, but the resource is precise enough to identify.

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?

Usage is implied by the read framing, and the retry guidance ('Preserve the private idempotencyKey for retries') covers a real operational case. There is no when-to-use vs when-not statement and no pointer to sibling methods for related reads.

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