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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false. The description adds concrete behavioral context beyond the annotations by disclosing the cost ($0.005 USDC via x402), which is non-obvious and important for an autonomous agent deciding whether to call the tool.

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?

A single, well-structured sentence conveys the purpose, the network, the meaning of the returned value, and the cost. Every clause earns its place and there is no redundancy.

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 parameterless, read-only, non-destructive tool with no output schema, the description is complete. It tells the agent what it will get (latest Base mainnet block number), the cost, and that it is a read-only operation.

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?

The tool has zero parameters, so the description has no parameter semantics to clarify. This matches the baseline of 4 for parameterless tools; no additional explanation is needed.

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 ('Get'), a precise resource ('current Base mainnet block number'), and clarifies it means 'latest chain height'. It clearly differentiates this from sibling tools like base_transaction or base_receipt by focusing on the live chain tip.

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 phrase 'current Base mainnet block number (latest chain height)' clearly implies the appropriate use case: an agent needing the current block height on Base mainnet. It does not explicitly name alternatives or exclusions, but for such a simple, well-scoped operation, the context is evident.

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