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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and openWorld, so the safety profile needs no restating. The description adds that values are averages over a lookback window and maps to a REST endpoint, but says nothing about response shape, granularity of the series, or rate limits. Useful but thin beyond the 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 core purpose is front-loaded in the first sentence with no padding, and the docs link plus REST operation line are compact reference aids. Slight redundancy in restating the time-period scoping, but nothing that wastes meaningful space.

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 one fully described parameter, complete annotations, and an existing output schema, the description covers what an agent needs to invoke the tool correctly. The remaining gap is non-essential context such as aggregation granularity, which the output schema likely conveys.

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% and the single time_period parameter has a full enum listing with an example, so the schema already carries the semantics. The description only restates 'for a time period' and adds no format or interpretation detail beyond the schema. Baseline 3 applies.

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 verb and resource ('Get average block sizes and weights') plus the aggregation scope ('for a time period'), so an agent knows this returns averaged aggregates rather than a single block. It does not contrast itself with nearby siblings such as get_block_fees, get_block_fee_rates, or get_blocks, which also return block-level metrics.

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?

There is no guidance on when to choose this over get_block_fee_rates, get_block_fees, or get_blocks, and no exclusions or prerequisites are given. The only implied usage cue is the 'time period' phrasing, which suggests trend/aggregate queries rather than point lookups.

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