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

With annotations present, the description adds real behavioral context the annotations cannot: the call costs $0.001 in USDC on Base via x402 and is billed per successful call, which also explains why readOnlyHint is false despite being a data lookup. It does not cover failure behavior, latency, 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 tight sentences, front-loaded with what the tool returns, followed by usage and cost. Every clause earns its place, including the cost line, which is non-obvious and material to invocation.

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?

No output schema exists, so enumerating the returned fields (hash, timestamp, tx count, gas used/limit, base fee in gwei, producer) is essential and present. Parameter and payment behavior are covered; only edge cases such as invalid block numbers or payment failure handling are unaddressed.

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 single 'number' parameter is already documented as 'Block number, or latest (default)'. The description repeats the same number-or-latest semantics without adding format details (hex vs decimal, block tags), 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?

Names a specific resource and scope (a block on Polygon PoS, by number or latest) and enumerates the returned fields, which lets an agent tell it apart from eth_block/arb_block/base_block by chain. It stops short of explicitly stating it is not for other chains, so sibling differentiation is implicit rather than stated.

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?

'Use for timestamps, confirmations and chain-activity checks' gives clear positive context for when to reach for this tool. There is no explicit when-not guidance or named alternative (e.g. polygon_tx for transaction-level lookups), so it does not reach the top of the scale.

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