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

Annotations already cover read-only, idempotent, open-world, and non-destructive behavior. The description adds valuable non-obvious behavior: it uses two real header timestamps, does not smooth stalls, charges $0.001 USDC per call, and is byte-identical to a REST endpoint. No contradiction with annotations.

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 compact and well-ordered: metric first, then the key behavioral differentiator, cost, supported chains, and REST equivalence. Every sentence earns its place and there is no filler or redundant schema repetition.

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?

Given the output schema exists and annotations cover safety/idempotency, the description is complete enough for an agent to call the tool correctly: it names required chain values, default window parameter, cost, and REST endpoint behavior. The only minor gap, exact bounds for 'blocks', is already disclosed as 'bounded' in the schema.

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%, so the baseline is 3. The description mostly restates the chain list and window concept already present in the schema; the REST query example ('chain=base&blocks=20') is mildly useful but does not add new parameter constraints or format details beyond the schema.

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 states a specific metric ('Seconds per block and blocks per hour') and the exact method ('timestamps of two real headers at the edges of a window'), which clearly identifies the resource as a raw block-cadence measurement. It also distinguishes itself from smoothed alternatives by noting that a stalled block widens the span rather than being averaged away, helping an agent separate it from siblings like chain_block_series.

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?

It gives concrete operational context: supported chains, cost per call, and byte-identical REST endpoint equivalence, which makes invocation expectations clear. It does not explicitly name alternatives or state when not to use this tool, though the 'instead of being smoothed away' clause implies a preference for raw cadence measurements.

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