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

Annotations already declare the safety profile (readOnlyHint=false, idempotentHint=true, openWorldHint=true, destructiveHint=false), and the description adds genuinely new behavioral context: the call costs 0.005000 test USDC on eip155:84532 and the idempotencyKey must be preserved for retries. However, the 'Read' framing sits in mild tension with readOnlyHint=false, and the description says nothing about return semantics or rate limits.

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, front-loaded sentences that move from purpose to cost to retry handling with no padding. The final sentence largely duplicates what the schema already says about idempotencyKey, which is the only mild waste.

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 paid RPC proxy with no output schema, the description covers the tricky bits (payment amount, chain, idempotency handling) but omits what the call returns and what the two required positional parameters mean. It is adequate but leaves real gaps.

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 only 50%: idempotencyKey is documented in the schema while the positional params array (block hash + uncle index) is not. The description repeats the idempotencyKey guidance already in the schema and adds nothing about the two positional parameters, so it fails to compensate for the coverage gap.

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 states a verb ('Read') and a concrete resource (eth_getUncleByBlockHashAndIndex on eip155:1), so an agent can distinguish it from sibling RPCs by name. However, it essentially restates the method name without explaining what the call actually does (return the uncle block at a given index for a block identified by hash), so the purpose is only weakly conveyed.

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 guidance on when to use this tool versus close siblings such as eth_getUncleByBlockNumberAndIndex, eth_getUncleCountByBlockHash, or eth_getUncleCountByBlockNumber. The only context given (cost, idempotency) concerns invocation mechanics, not tool selection.

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