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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true and idempotentHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: a nonexistent block returns 404 and is uncharged, and each call is billed so repeats are not free (which explains the non-idempotent hint). It does not describe response shape or pagination, but with annotations carrying the safety burden this is solid added value.

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 the core purpose and return fields, then usage routing, then edge case and pricing. Dense but every clause carries information; the pricing/free-tier sentence is the longest and is the least essential to correct invocation.

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?

There is no output schema, so the description compensates by enumerating the returned fields. Combined with the 404 behavior, pricing, and the sibling pointer, an agent has everything needed to call this correctly.

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 schema already documents 'number' with the 'latest' default, so the baseline is 3. The description adds a concrete example (number=latest) and clarifies that a block may be given as a decimal number, which is slightly more than the schema states.

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 ('Latest block number and block details on Scroll, or any block by decimal number') and enumerates the returned fields (hash, timestamp, tx count, gas used/limit, base fee, producer). It also names the sibling it is not (scroll_gas), so an agent can distinguish it from the other scroll_* tools without opening a 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?

Explicitly says when to use it ('for timestamps and confirmation counts') and routes the agent elsewhere for the adjacent need ('for current fees use scroll_gas'). The 'number=latest' example further anchors typical invocation.

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