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

Annotations already declare read-only, non-destructive, open-world and non-idempotent, so the safety profile is covered. The description adds genuinely new behavioral context: per-call pricing, the 25-free tier, free failed calls, and an explicit note that repeats are not free because each call is charged, which explains the non-idempotent hint. It stops short of describing response shape or pagination, but no output schema exists and the fields are enumerated.

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?

Front-loaded with what is returned, then the field list, then usage routing, then error and pricing notes. Dense but nearly every clause carries information; the pricing sentence is slightly long but materially affects repeated-call decisions.

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?

With no output schema, the description compensates by enumerating the returned fields, and it also covers default behavior ('latest'), the 404 failure mode, and cost. Nothing an agent needs to invoke this correctly 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?

Schema coverage is 100% and the single parameter is already documented as 'Block number, or latest (default)', so the baseline is 3. The description adds real meaning on top: the number must be decimal, and it supplies a concrete example (number=latest), which prevents an agent from passing a hex block tag.

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?

Names a specific verb and resource (fetch latest block number or any block by number on Berachain) and enumerates the returned fields: hash, timestamp, tx count, gas used/limit, base fee, producer. It explicitly distinguishes itself from the sibling bera_gas, so an agent can route without opening either 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?

States the intended use cases (timestamps and confirmation counts) and names the alternative for the adjacent need ('for current fees use bera_gas'). It also covers the failure case: a block that does not exist yet returns 404 and is uncharged.

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