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

With no annotations, the description carries the full burden, and it does useful work: it discloses the payment model ('0.001 USDC per call over x402 on Base'), which an agent must know before invoking, and it lists the returned data fields since there is no output schema. It omits any note on error behavior, rate limits, or freshness/latency guarantees.

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?

Two tight sentences plus a short pricing line; purpose is front-loaded and nothing is padded. The only wart is the redundant repetition of 'on Base' in the first and last sentences.

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 zero-required-parameter read tool with no output schema, the description covers what is needed: the data returned, when to call it, and the cost. The one gap is whether the optional 'chain' parameter permits anything other than Base, since the description implies Base-only while the schema suggests a variable chain.

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 there is only one optional parameter, so the baseline is 3. The description's 'on Base' does weakly constrain the chain value, but it adds no syntax, allowed values, or default behavior beyond what the schema's 'Example: base' already conveys.

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-and-resource pairing ('Block number on Base') and enumerates exactly what is returned: block height, timestamp, age, base fee, gas used, transaction count. It does not explicitly differentiate itself from siblings like evm_gas or evm_tx, so it lands at 4 rather than 5.

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?

The sentence 'Use it when an agent needs the current block number or the chain head' gives a clear, affirmative usage context. It does not name alternatives or when-not-to-use conditions (e.g., 'for gas estimates use evm_gas'), so it stops short of full routing guidance.

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