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

The description is highly transparent, disclosing costs ($0.01/call), usage constraints (first 25 free), failure modes (returns 404 for non-existent blocks), and operational status (reads or computes only and changes nothing). This adds significant value beyond the provided annotations and hints.

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 comprehensive yet efficient; every phrase delivers critical information, whether it's detailing return data, usage scenarios, cost structure, or safety guarantees. It is densely packed with high-value information.

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?

Given the lack of an output schema, the description successfully acts as a comprehensive documentation, detailing the expected data returned (hash, timestamp, gas used, etc.), the handling of edge cases (404), and operational costs. No major piece of information required for a successful invocation is 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?

While schema coverage is 100%, the description adds vital semantic context by explaining that the input 'number' can be a decimal block number or the string 'latest,' and provides a concrete usage example (number=latest). This is helpful despite the schema being complete.

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 clearly identifies the function: retrieving 'Latest block number and block details on zkSync Era, or any block by decimal number.' It is highly specific and distinguishes itself from sibling tools by focusing on block-specific data.

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?

It provides explicit guidance on usage: 'Use for timestamps and confirmation counts; for current fees use zksync_gas.' This tells the agent exactly when to prefer this tool over `zksync_gas` or other related functions.

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