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

Annotations already cover readOnly/idempotent/openWorld, and the description goes well beyond them: it lists every returned field, explains Parallax-specific semantics (epochStartTime at multiples of 2016, 600-second target block time), flags extraData as untrusted text, and discloses a hard 200-transaction cap with a transactions_truncated marker. That is exactly the kind of operational context annotations cannot convey.

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 block lookup modes before the long return-field inventory, and the transaction-detail and truncation caveats come last where they belong. The field enumeration is dense but every clause carries information; a slightly tighter grouping of the return fields would make it fully optimal.

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 and no annotation coverage of return values, the description carries the full burden and does so thoroughly, describing fields, units, truncation behavior, and data-trust caveats. Nothing an agent needs to call this correctly or interpret the result 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 already documents both parameters, so the baseline would be 3. The description earns extra credit by detailing what full_transactions actually yields (from, to, value in wei and LAX, gas price, nonce, calldata selector) and by stating the 'latest' default and the 200-item truncation limit, which the schema omits.

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 opening sentence names a specific verb+resource ('A block by number, hash or "latest"') and enumerates all three accepted lookup modes, which cleanly separates it from siblings like get_transaction, get_receipt, and wait_for_new_block. An agent can identify the tool and its input contract without opening the 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?

Three concrete invocation examples show how to call it and the full_transactions toggle is explained, which implies the usage context (historical/point lookup). However, it never states when to prefer this over siblings such as wait_for_new_block for real-time needs or block_reward for subsidy-only queries, so no explicit alternative routing is given.

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