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

Annotations already cover safety (readOnly/idempotent/non-destructive/openWorld), yet the description adds material context beyond them: the 60-90 second expiry window, what the return payload contains, and a concrete rate-limit/cost model (25 free calls/day, then $0.01 USDC via x402). That is exactly the kind of pricing and lifecycle disclosure the rubric rewards.

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?

Front-loaded with the timing guidance and the returned values, and every sentence carries usable information (expiry, return shape, cost, docs pointer). The 'Inputs: network...' sentence redundantly restates the schema, which is the only real slack.

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 carries the burden of describing returns, and it does (fresh blockhash, blocks left, seconds left). Cost, default network, and call timing are all present, leaving nothing essential an agent needs 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 description coverage is 100% and the schema's network field already documents the default and devnet/mainnet distinction in detail. The description largely repeats that ('Default "mainnet-beta" (real money)') without adding syntax or meaning beyond the schema, so the baseline 3 applies.

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+contents: it returns a fresh blockhash plus blocks-remaining and seconds-remaining before expiry. This is clearly distinguishable from every sibling (balance, fee, check_tx, history, etc.), none of which returns a blockhash. An agent can identify this tool without opening the 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?

"Run right before building a transaction you'll sign" gives explicit timing for when to call it. No when-not-to-use guidance or named alternative is provided, but no sibling competes for this purpose, so context is clear though not exhaustive.

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