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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds genuinely new context the annotations cannot carry: the ~60-90 second expiry window, the metered cost (25 free calls/day, then $0.01 USDC per call via x402), and where output semantics are documented. The cost/rate-limit disclosure is particularly valuable and would otherwise be invisible.

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 operative instruction and the time-sensitivity constraint are front-loaded in the first two sentences, followed by output expectations and cost. Most sentences earn their place, though 'Example: {}.' is filler that conveys nothing and slightly dilutes the structure.

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?

There is no output schema, so the description bears the return-value burden and does describe the payload (a fresh blockhash, blocks remaining, approximate seconds remaining). Combined with the cost and expiry context, an agent has enough to call this correctly; the pointer to external docs for 'outputs explained' is a minor reliance on off-tool documentation.

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 100% and the single 'network' parameter already documents its enum, default, and the real-money vs test-wallet distinction. The description says nothing about the network parameter and adds no syntax or default information beyond the schema. Baseline 3 is appropriate when the schema carries the whole load.

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 specific verb+resource: it returns a fresh blockhash plus the blocks and seconds remaining before expiry. That is clearly distinct from every sibling (balance, check_tx, fee, tokens, etc.), none of which deal with blockhashes. It is only slightly muddied by leading with an imperative ('Run just before building a transaction to sign') rather than naming the artifact first.

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?

It gives an explicit trigger condition ('Run just before building a transaction to sign') and quantifies the operative constraint ('expire in about 60-90 seconds'), which tells the agent precisely when this call is and isn't worth making. No alternative tool is named, but no sibling performs this function, so there is nothing to route away to.

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