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

Annotations cover the read-only and open-world nature of the call, and the description adds non-obvious behavior: the call is metered at $0.01 USDC on Base via x402. Cost/payment disclosure is real added value beyond the annotations, though the mechanics of the payment flow itself are not described.

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 short sentences, front-loaded with the lookup scope and output fields, followed by the pricing note. No filler or restatement of the tool name.

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 single-parameter read tool with no output schema and light annotations, the description supplies the accepted inputs, the tags, the key return fields, and the cost. It omits details such as whether unnamed/default behavior exists when 'block' is omitted, which the empty required list makes relevant.

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 0%, so the description must carry the parameter burden. It does so by documenting that 'block' accepts either a numeric block number or a named tag, and it enumerates the valid tags (latest, safe, finalized), which the schema alone does not.

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 ('block lookup by number or tag') and enumerates the returned fields (timestamp, gas, transaction count), which clearly separates it from siblings like base_tx or base_receipt. An agent can identify the tool without opening the schema.

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 explicit guidance on when to use this versus alternatives such as base_tx, base_receipt, or base_gas. The only usage-adjacent information is the accepted input forms (number or tag), which is closer to parameter documentation than selection guidance.

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