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

Annotations cover safety traits (readOnlyHint=false, idempotentHint=true, destructiveHint=false, openWorldHint=true), but the description adds genuinely useful context not present in them: the exact cost (0.002500 test USDC), the payment chain (eip155:84532), and the requirement to persist the idempotency key before payment and reuse it only for retries. This pricing/payment behavior is valuable operational disclosure.

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 clauses, front-loaded with the operation, then cost, then the idempotency instruction. Efficient and easy to parse, though the opening clause largely duplicates the tool name rather than adding substance.

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?

For a low-complexity 2-parameter proxy call with no output schema, the description covers the operational essentials (chain, cost, idempotency handling). However, it omits what the call returns (a hex quantity for the transaction count) and clarification of the block parameter, leaving a modest gap.

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 description coverage is 50%: the idempotencyKey is documented in the schema, but the core 'params' block-number/tag argument has no description. The description only reinforces the idempotency key rule and says nothing about the block-number-or-tag semantics, which is the parameter an agent most needs to understand.

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 says 'Read eth_getBlockTransactionCountByNumber from Ethereum (eip155:1),' which essentially restates the tool name rather than explaining what the method returns (the count of transactions in a block for a given block number/tag). It does not distinguish this from the sibling ethereum_eth_getBlockTransactionCountByHash, so an agent gets little beyond the method identifier it already sees in the name.

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?

There is no statement of when to use this tool versus the ByHash sibling or other block-inspection tools. The only procedural note is 'Preserve the private idempotencyKey for retries,' which addresses retry behavior but not tool selection or prerequisites.

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