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

With no annotations, the description carries the behavioral burden itself. It adds two useful behavioral details: the cost consequence (pay-per-call $0.005 USDC) and the response contents (hash, timestamp, tx count, gas used, base fee). It does not cover edge cases such as behavior when the optional number parameter is omitted, but for a read-only block lookup this is a relatively minor gap.

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 two short, front-loaded sentences with no filler. It packs the resource, accepted input, return fields, and pricing into a compact form that is easy to scan.

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-only tool with no output schema, the description covers the essential invocation requirements: which block to request, what data will be returned, and the cost of the call. It omits error behavior and optionality details, but the provided information is likely sufficient for correct invocation in most normal use cases.

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% — the number parameter is already described as 'Block number or "latest"' — so the baseline is 3 because the schema already does the heavy lifting. The description adds little parameter-specific context beyond restating the accepted value and does not clarify whether omitting number is allowed or what default would be used.

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 identifies a specific resource (a Polygon block by number or 'latest') and lists the returned header fields, so an agent can tell it apart from sibling token, balance, and transaction tools. However, it uses a noun phrase rather than an explicit verb and does not contrast with the similarly named base_block sibling, relying mainly on the polygon prefix for disambiguation.

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 description states accepted input values and the pay-per-call cost, but gives no guidance about when to choose polygon_block over alternatives such as polygon_tx or base_block. There are no prerequisites, exclusions, or explicit routing conditions.

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