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

With no annotations, the description carries the full behavioral burden. It discloses that the operation reads data, returns both decimal and hex formats, and has a free-trial limit tied to a signed wallet, but it omits details about authentication requirements, error behavior, and what happens after the trial.

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 description is short, front-loaded with the action, and avoids unnecessary detail. The 'Block Number:' prefix is slightly redundant with the tool name, and the trailing trial/pricing note, while useful, reads as promotional.

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 simple read-only tool with one parameter and no output schema, the description covers purpose, source, return format, and trial cost. However, it does not explain valid chain values, whether the chain parameter is required, or the full authentication/payment flow, leaving gaps an agent would need to resolve by trial.

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 schema has one parameter ('chain') with 0% description coverage. The phrase 'selected chain RPC' implies the parameter chooses which chain to query, but no valid values, default chain, or requiredness are specified, leaving significant semantic gaps.

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 ('Fetches'), resource ('latest block number'), source ('selected chain RPC'), and return format ('decimal and hex'). It is clear what the tool does, but it does not explicitly differentiate itself from siblings like x402-rpc or x402-block-explorer, so it falls short of a 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?

There is no guidance on when to use this tool versus alternatives such as x402-block-explorer, x402-rpc, or x402-chain-id. The free-trial mention is promotional rather than usage guidance, and no prerequisites or exclusions are stated.

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