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

Goes well beyond the annotations by disclosing return semantics ('block' and 'next_block', or 'is_latest: true'), error behavior (422 before genesis and 5xx are not charged), latency (~1-3 s / 3-6 reads), pricing, free-tier limits, and docs. This is rich behavioral context for a paid read-only API.

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 purpose is front-loaded and every sentence carries operational information: return shape, error cases, timing, cost, and docs. It is slightly dense and could be structured with bullets, but remains efficient and non-redundant.

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?

Covers what an agent needs: supported chains, alternative tool for latest block, return fields, error conditions, latency, pricing, free-tier limits, and docs. Even with an output schema present, the description provides sufficient context to invoke it 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 description coverage is 100%, so the schema already documents chain enum and timestamp formats. The description adds chain names and the Base genesis edge case, but no timestamp syntax beyond what the schema provides. Baseline 3 is appropriate.

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: 'find the block at a point in time' on named chains. It distinguishes the tool from the sibling get_block_number by explicitly routing latest-block queries there. An agent can tell exactly what this tool does 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?

Explicitly names the alternative for retrieving the latest block: 'For the latest block use get_block_number.' It also clarifies supported chains and the invalid-time case (422 before_genesis), so the agent knows when this tool applies and when not to use it.

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