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

Annotations already cover read-only, non-destructive, open-world, and crucially idempotentHint=false; the description adds real context beyond that by explaining the pricing model (charged per call, repeats not free), the 404-and-uncharged behavior for non-existent blocks, and the free-failure policy. That materially explains the non-idempotency and error semantics. Minor gap: no guidance on which block ranges are valid or how far back Gnosis queries are supported.

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 resource and returned fields, then routing, then behavioral caveats, then pricing. The pricing/billing sentence is long and partially boilerplate, but it is load-bearing for a paid, non-idempotent call, so it earns its place.

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 optional-parameter read tool with no output schema, the description covers what is returned, when to use it, the error case, and the billing model. An agent has everything needed to call it correctly and to decide whether to call it at all.

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 already documents 'latest' as default, so the baseline is 3. The description earns a bit more by specifying the number must be decimal and giving an inline example (number=latest), which the schema does not state.

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+resource (retrieve latest or a numbered block on Gnosis) and enumerates the returned fields: hash, timestamp, tx count, gas used/limit, base fee, producer. It also names the sibling it is not (gnosis_gas) so the agent can distinguish it from the fee-oriented tool 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?

Explicit routing guidance: 'Use for timestamps and confirmation counts; for current fees use gnosis_gas.' This gives both the positive use case and the alternative tool with the condition that selects it, leaving little to inference.

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