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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, and the description adds genuinely useful non-schema facts: a pending or unknown hash returns 404 uncharged, pricing at $0.01/call with first 25 free, failed calls free, and that repeats are charged (which motivates idempotentHint=false). That is real added context, but the price/auth material is commercial boilerplate rather than tool behavior; a 3 reflects solid but partly promotional 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?

Purpose and return fields are correctly front-loaded, but the tail of the description dilutes into pricing, payment rails, and free-tier policy. That information is useful once but crowds out nothing structurally and is longer than needed for a single-parameter read tool.

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 one required parameter and no output schema, the description compensates by listing exactly which receipt fields are returned, plus the failure mode (404, uncharged) and the sibling to use for other fields. Nothing an agent needs to call it correctly is missing.

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 the schema already documents the hash format, so the baseline is 3. The description adds a concrete worked example hash ('0xc0003ffe...'), which makes the expected 0x-prefixed 64-hex shape unambiguous and is worth a point above baseline.

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+resource ('Transaction receipt on zkSync Era (eth_getTransactionReceipt)') and enumerates what it returns: status, gas used, effective gas price, fee in ETH, log count, contract created. It explicitly contrasts itself with the sibling zksync_tx, so an agent can route between them without opening either schema.

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?

Gives a concrete use case ('confirm a payment or call went through') and names the alternative with its selection condition ('for sender, value and calldata use zksync_tx'). The pending/unknown hash behavior is also stated, so failure conditions are predictable.

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